How much do you know about the M3 engine? There are quite a few M3's running 100-150 shots (as most say they don't notice much with a 50 shot). I've seen a 200 shot setup on a M3 a while back.

 

I hate to say this, but those M3's are pretty nasty track cars too.

 

E46 M3 is a little on the heavy side stock, however, they are great handling cars and they are by no means sluggish around the track, as a matter of fact, I have to agree w/ afterburn27 that they are nasty track cars as well. S54 motors are fantastic motors, but not sure how good they can hold up under nitrous abuse. The guy has been using 150 shots for about a year now with no signs of his motor going anytimes soon. 200 shots probably need to pull lots of timing though.