SC blow off valve?

I am getting ready to put a smaller pully on my supercharger and a buddy of mine said that some SC's have a blow off valve that goes off if you run too high of psi, thus your not really gaining any HP. Does anyone know if the 00-05 SC's on these 3800 II motors have one? Im not tryin to put a smaller pully on there if it isnt going to help me any.

2nd, whats yall's opinion on the thrasher cold air intake, and is borla exahust really worth the money?

B.R