Look at your SC snout, by the pulley. If you see a bunch of black stuff around there, good chance your belt is slipping. If you're using the stock size belt with a 3.4, I can just about guarantee it's slipping. Which may actually be helping you, belt slip = less boost = less KR. 605's is what I run in my GT, I wouldn't use them with anything smaller than a stock pulley, but that's just me. You also want as wide of a gap as you can run w/out spark blowout, this will vary so you have to play with it a bit. .055 is a good place to start, if you need to go lower do it, but .045 is like nitrous small.
