$225,000?!?!
I would race this guy just for the fun of it. Who knows, maybe you'll be able to pull something out. I can believe that this guy has 600hp due to the fact that he states he has that kind of money invested in the car. Either way, I think you are in for a tough race -- whether he is modded or not. 911 TT trap in the 116-120mph range if I remember correctly (unmodified).
I think you will have a good advantage racing w/ slicks against his AWD stock tires. With a good launch, you should put a few cars on him to start. The question is, will he be able to run you down?
Let us know how it turns out! Good luck!