you shouldnt have problem with your law suit if he listed it as a DOHC, if its truely an Si (rear disk conversion?), and he didnt tell you it had the Y8 and not the B16. Not sure what you can do other than sue for return of the car and get your money back or try to get some money out of him. However, deciding how much the car is worth without the B16 is going to be tough and even harder to prove in court. I'm interested to see what the VIN number is...