You are now in a pickle! Did you sign the financing app? If you did with the false figures, then you may have broken some federal and state laws. Normally you need to sign it that states what your income is! Typing in the wrong name for the co-buyer will not necessarily enough to get you out especially if the co-buyer signed it. Who is this car company? You really should call a lawyer and talk over you case in detail.
By signing you have asserted that that information is true. You may have broken some laws. As to getting out of the contract you do not have clean hands since you asserted that false information was true. I think your stuck. Your not going to want to go into court and admit that you did this.