I have a 2.3 whippled termi @ 19psi with stock manifolds and a pro chamber and borla stingers. Best / newest dyno sheet is 624 uncorrected with new tune right before i bought the car and others in the 570s. I am gonna put long tubes on it and was figuring going with ahr 1 3/4 primaries and 2 1/2 collectors and there catless x. When I just called the to get the part # they really recomended there 3 inch collector and x pipe that goes from 3 to 2 1/2. The car is pretty low with h&r race springs and no isos so im a little worried about ground height and if it really needs a 3 inch collector since its going into a 2 1/2 exhaust anyway?. wondering what you guys with 600+ are running for collectors.