sorry i was away on the weekend.
Here are some more details. The guy said he has 480 at the crank. No, he does not have a blower (i've seen under the hood). We are both manual 6spd (No, I didn't granny shift, and if anything i shifted better than him). I did pull on him, but barely, started with 3rd at around 90mph, and by 140 I was maaaybe 2 cars ahead.
He has some optional gearing in the diff (not sure what kind, but he said it's for better 1/4mile).
We were heading to the ring, and I rode with him one lap(as did he)... the mustang is a completely different beast. As we both agreed the M3 sticks a LOT better, and stays more composed through the corners. Mustang tended to get the rear out, or spin the tires (the rear felt very unstable).
Another example, there was C63 black series on the track (had one passenger, while i had 2 heavy weight passengers(maybe extra 350pds)), and on the straight that C63 raped me.
Reading all the comments, I am concerned. I will desparetly look for a dyno to make sure i'm putting the correct power down. From my dyno butt, the car is A LOT faster than what I had before....