Exhibit 99.4

UNAUDITED PRO FORMA COMBINED FINANCIAL STATEMENTS

The following unaudited pro forma combined balance sheet combines the consolidated historical balance sheet of Format, Inc. and the consolidated historical balance sheet of The W Group, Inc., a Delaware corporation (“The W Group”) as of March 31, 2011, following the completion of a reverse merger transaction (the “Reverse Merger”), in which PSI Merger Sub, Inc., (“Merger Sub”) a Delaware corporation that was newly-created as a wholly-owned subsidiary of Power Solutions International, Inc. (f/k/a Format, Inc.) (the “Company”) merged with and into The W Group, and The W Group remained as the surviving corporation of the Reverse Merger, becoming a wholly-owned subsidiary of the Company. Concurrent with the closing of the Reverse Merger, the Company completed a private placement (“Private Placement”) of shares of its newly designated Series A Convertible Preferred Stock and warrants to purchase shares of the Company’s common stock for gross proceeds of $18,000,000 and the Company completed the refinancing of its bank debt (“Bank Refinancing”). The pro forma combined balance sheet presented herein reflects the effects of the Reverse Merger, Private Placement and Bank Refinancing (collectively the “Transactions”) as if they had been consummated on March 31, 2011. The following unaudited pro forma combined statement of operations combines the historical statements of operations of Format, Inc. and The W Group for the three months ended March 31, 2011, giving effect to the Transactions, as if they had occurred on January 1, 2010.

The following unaudited pro forma combined financial statements are presented to illustrate the estimated effects of the Transactions. The unaudited pro forma combined financial statements were prepared using the historical financial statements of Format, Inc. and The W Group as of and for the three months ended March 31, 2011.

The historical financial information has been adjusted to give effect to pro forma events that are directly attributable to the Transactions and factually supportable. Additionally, the pro forma adjustments related to the statement of operations are expected to have a continuing impact on the combined results and are based on available data and certain assumptions that we believe are reasonable.

The following information should be read in conjunction with the pro forma combined financial statements.

The unaudited pro forma combined financial statements are presented for informational purposes only. The pro forma information is not necessarily indicative of what the financial position or results of operations actually would have been had the Transactions been completed at the dates indicated. In addition, the unaudited pro forma combined financial statements do not purport to project the future financial position or operating results of the combined company.

The unaudited pro forma combined financial statements were prepared using the reverse acquisition application of the acquisition method of accounting as described in ASC 805-40-05-2, with The W Group treated as the acquiror for U.S. GAAP accounting and financial reporting purposes. Accordingly, the unaudited pro forma combined financial statements are presented as a continuation of The W Group’s financial statements with an adjustment to reflect the issued equity capital of the former Format, Inc., the legal parent, including the equity issued by the Company to effect the business combination.

UNAUDITED PRO FORMA

COMBINED BALANCE SHEET

OF

POWER SOLUTIONS INTERNATIONAL, INC.

MARCH 31, 2011

(Dollar amounts in thousands)

UNAUDITED PRO FORMA

COMBINED STATEMENT OF OPERATIONS

OF

POWER SOLUTIONS INTERNATIONAL, INC.

THREE MONTHS ENDED MARCH 31, 2011

(Dollar amounts in thousands in per share data)

NOTES TO UNAUDITED PRO FORMA

COMBINED FINANCIAL STATEMENTS

On April 29, 2011, Power Solutions International, Inc. (f/k/a Format, Inc.) (the “Company”) completed a reverse merger transaction (the “Reverse Merger”) pursuant to an agreement and plan of merger (the “Merger Agreement”), in which PSI Merger Sub, Inc., a Delaware corporation that was newly-created as a wholly-owned subsidiary of the Company (“Merger Sub”), merged with and into The W Group, Inc., a Delaware corporation (“The W Group”), and The W Group remained as the surviving corporation of the merger, becoming a wholly-owned subsidiary of the Company. As a result, the historical financial statements of The W Group constitute the historical financial statements of the merged companies. The transaction is considered to be a capital transaction and as such is the equivalent to the issuance of common stock by The W Group for the net monetary assets of Format, Inc. accompanied by a re-capitalization. For accounting purposes, The W Group is treated as the continuing reporting entity.

Concurrent with the closing of the Reverse Merger, pursuant to a purchase agreement (the “Purchase Agreement”), the Company completed a private placement (“Private Placement”) of shares of its newly designated Series A Convertible Preferred Stock, liquidation preference of $1,000 per share (“Company Preferred Stock”), together with warrants (“Private Placement Warrants”) to purchase shares of the Company’s common stock (“Company Common Stock”), to accredited investors, receiving total gross proceeds of $18,000,000 at the closing of the Private Placement. The incremental costs of the transaction incurred by The W Group will be charged pro rata to equity and expenses based on the cash received and allocated between the Company Preferred Stock and the Private Placement Warrants. The transaction costs incurred by Format, Inc. (i.e., the Company prior to the closing of the Reverse Merger, which is also referred to herein as “Format”) will be expensed.

In connection with the Reverse Merger and the Private Placement, the Company entered into a stock repurchase and debt satisfaction agreement (“Repurchase Agreement”) with Ryan Neely, Format’s sole director and executive officer immediately prior to the closing of the Reverse Merger, and his wife, Michelle Neely. The Company repurchased 3,000,000 shares of Format common stock from Ryan Neely and Michelle Neely, which represented approximately 79.57% of the shares of Format common stock outstanding immediately prior to the Reverse Merger and the Private Placement (without giving effect to the 1-for-32 reverse stock split of the Company Common Stock to be consummated pursuant to the Purchase Agreement following the consummation of the Reverse Merger and the Private Placement (the “Reverse Split”)), and immediately thereafter these shares were cancelled, and Ryan Neely and Michelle Neely terminated all of their right, title and interest in and to, and released Format from any and all obligations it had with respect to, the loans made by Ryan Neely and Michelle Neely to Format (which as of March 31, 2011 was approximately $114,000), in exchange for a cash payment of $360,000. As part of the Repurchase Agreement, Ryan Neely also released Format from any other obligations owed to him which includes the balance of accrued liabilities on Format’s balance sheet of approximately $50,000.

The Reverse Merger and Private Placement occurred in a series of steps outlined below:

There were no inter-company balances and transactions between Format, Inc. and The W Group as of the dates and for the periods of these pro forma combined financial statements, except for the payment of $20,000 in March 2011 by The W Group to Format as consideration for the extension of a deadline for the consummation of the Reverse Merger and related transactions, which has been eliminated in the pro forma financial statements.

The pro forma combined provision for income taxes does not necessarily reflect the amounts that would have resulted had Format, Inc. and The W Group filed consolidated tax returns during the periods presented. The pro forma adjustments included in the unaudited pro forma combined financial statements are as follows:

Pro Forma Combined Balance Sheet Adjustments

Pro Forma Combined Statement of Operations Adjustments

The Company computes earnings per share by applying the guidance stated in ASC 260, Earnings per Share, to determine the net income (loss) available per share of its common stock. Pro forma earnings per share is calculated as if the Reverse Merger had occurred as of January 1, 2011, using the two-class method before taking into account the Reverse Split, because the convertible preferred shares participate in any undistributed earnings with the common shareholders. Upon the Reverse Split, the shares of Company Preferred Stock automatically convert to shares of Company Common Stock, as such, the pro forma net income (loss) per share is then calculated under the standard method, as consolidated net income available to common shareholders divided by the weighted average shares of Company Common Stock of Format, Inc. (the legal acquiror) immediately after the Reverse Split, which is also presumed to have occurred as of

January 1, 2011. Diluted earnings per share, under both methods, is calculated by evaluating the dilutive effect of potential shares of Company Common Stock issuable per the terms of the Private Placement Warrants and the Roth Warrant.

Series A Convertible Preferred Stock

The Company Preferred Stock is convertible at the option of the holder at any time, subject to limitation based upon the shareholder’s proportion of the available shares for conversion, and will automatically convert to common shares upon effectiveness of the Reverse Split at a conversion price of $12.00 per share ($0.375 pre-Reverse Split). The conversion of all the preferred shares could be considered contingent upon a substantive event other than market price triggers, which, per ASC 260-10-45-43, requires that the converted shares not be included in diluted EPS until such time that the contingency, (in this case, shareholder approval of the Reverse Split) has been met. However, approval of the Reverse Split is controlled by the majority shareholders of the Company, who have agreed to vote in favor of the Reverse Split pursuant to voting agreements entered into in connection with the Reverse Merger and the Private Placement, and have therefore substantially resolved the contingency. Accordingly, all shares of Company Preferred Stock have been evaluated for their dilutive effect in the calculation of pro forma diluted EPS.

The Company Preferred Stock is subject to full-ratchet anti-dilution whereby, upon the issuance (or deemed issuance) of shares of Company Common Stock at a price below the then-current conversion price of the Company Preferred Stock, subject to specified exceptions, the conversion price of the Company Preferred Stock shall be reduced to the effective price of Company Common Stock so issued (or deemed to be issued).

The Purchase Agreement also contains the following provision, which may be deemed to be a form of anti-dilution protection. If prior to the earlier of (1) the second anniversary of the date on which the initial Registration Statement is declared effective, as described previously in this document and (2) 180 days after the closing of a firm commitment public underwritten offering of equity securities resulting in gross proceeds of not less than $15.0 million, the Company issues equity securities in a public or private offering (or series of related offerings) resulting in gross proceeds of at least $5.0 million at or below a pre-determined effective price per share (“Reset Price”), the Company will have to issue to each investor in the Private Placement (1) additional shares of Company Common Stock so that after giving effect to such issuance, the effective price per share of Company Common Stock acquired by such investors in the Private Placement will be equal to the Reset Price and (2) additional Private Placement Warrants covering a number of shares of Company Common Stock equal to 50% of the shares of Company Common Stock issued pursuant to clause (1) above. This event of market-based contingency does not exist until the Company issues securities in an offering resulting in a price below the Reset Price upon the terms set forth in the Purchase Agreement. Management’s discretion in this matter, and the inability to determine the variable number of additional common shares to be issued, makes the adjustment for these potential shares indeterminable until such events occur. Thus, such potential shares are not considered in the diluted EPS calculation.

Lastly, the Company Preferred Stock grants voting rights and participation rights to dividends on par with Company Common Stock, with 2% preference dividends payable should the Reverse Split not be effective within 120 days after the Private Placement. Because the Company Preferred Stock participates in undistributed earnings with Company Common Stock, it is considered as a participating security under ASC 260-10-45 until such conversion occurs. Accordingly, the Company will apply the two-class method to calculate per share amounts for distributed and undistributed earnings available to each class of stock.

Private Placement Warrants

For each share of Company Common Stock issuable upon conversion of shares of Company Preferred Stock purchased by investors in the Private Placement, investors in the Private Placement received warrants to acquire one-half share of the Company’s common stock at an exercise price of $0.40625 per share ($13.00 per share post-Reverse Split). An aggregate total of 24,000,000 shares (750,000 shares post-Reverse Split) can be initially purchased upon exercise of the Private Placement Warrants, but the Private

Placement Warrants are not exercisable before the effective date of the Reverse Split, which the majority shareholders have agreed to vote in favor of pursuant to voting agreements. The Private Placement Warrants are subject to full-ratchet anti-dilution whereby, upon the issuance (or deemed issuance) of shares of Company Common Stock at a price below the then-current exercise price of the Private Placement Warrants, subject to specified exceptions, the exercise price of the Private Placement Warrants shall be reduced to the effective price of Company Common Stock so issued (or deemed to be issued). The treasury stock method has been applied to determine the number of treasury shares assumed to be purchased from the proceeds of warrant exercises, with any residual shares representing the incremental shares of Company Common Stock to be issued and included in diluted EPS. The average market price of the Company Common Stock during the reporting period is used to approximate the number of treasury shares repurchased from the proceeds of an assumed warrant exercise. Since the Company Common Stock was not actively traded during 2010 and the first three months of 2011, a recent valuation performed by independent consultants has been utilized and assumed to have remained the same throughout the period. The appraised fair value of $10.08 per common share results in an excess number of treasury shares purchased over the number of shares issued upon exercise of the Private Placement Warrants at $13.00 per share; thus, the Private Placement Warrants were not considered dilutive securities.

Roth Warrant

A warrant representing the right to purchase initially 3,360,000 shares of Company Common Stock at an initial exercise price of $0.4125 per share ($13.20 per share post-Reverse Split) was issued to Roth Capital Partners, LLC in their capacity as placement agent in the Private Placement. The Roth Warrant is not exercisable before the effective date of the Reverse Split, and thereafter, is exercisable immediately, and has been evaluated for its potentially dilutive effect using the treasury stock method. An excess number of treasury shares could be purchased with the proceeds from exercise of the Roth Warrant, resulting in exclusion of the Roth Warrant from diluted EPS.

Following is the calculation of earnings per common share utilizing the two class method without effect to the Reverse Split:

(In thousands, except per share amounts)

Allocation of undistributed earnings (Basic and diluted per-share amounts):

Anti-dilutive potential common shares excluded from the diluted earnings per share computation:

Roth Warrant: 3,360,000 shares of Company Common Stock pre-Reverse Split; 105,000 shares post Reverse Split; exercise price $13.20 post-Reverse Split; average share price $10.08

Private Placement Warrants: 24,000,000 shares of Company Common Stock pre-Reverse Split; 750,000 shares post-Reverse Split; exercise price $13.00 post-Reverse Split; average share price $10.08

On a post-Reverse Split basis, the Company Preferred Stock will no longer exist, and with no other participating securities, the standard EPS calculation would apply.

Because the preferred shares are convertible automatically upon the effectiveness of the Reverse Split, which is substantially imminent, the preferred shares are substantively equivalent to common shares on a post-Reverse Split basis, and are included as such in the basic earnings per share calculation on this basis.

Following is the calculation of earnings per share on a post Reverse Split basis: