i had a thread on my "other forum" but its having issues since the upgrade
anyway
the downpipe (depending on if you get the catted or cat free version) basically eliminates the pinch point in the exhaust right before the cat, and some even delete the "Ubend" (look under your car where the pass door hinge is, its bent to accomidate the rear O2 sensor, most aftermarket DPs relocate it to the side to eliminate the "U bend"
heres my OLD intake setup, it actually extended into the fenderwell, but i removed that section to show the filter
Thats just painted pvc ( i recommend ABS Sewer wall pipe, holds better in the heat) Those fittings are just Fernco avail @ home depot, i recommend
www.hightempsilicone.com now though (you learn as you go right? lol) Hellfire Motorsports (
www.hellfiremotorsports.com) & Autozone also sell prebent sections of alum intake piping if you want to go that route.
the 180* t-stat lowers the temp @ which the thermostat opens, to help cool the engine/maintain cooler under hood temps, that paired w/ a pcm tune to match, you should notice 1-2 lines cooler on your temp gauge
Dropping pulley size: this gets a bit tricky, every 3800 i have seen modded acts differently, so the only TRUE way to know what a safe pulley size is, is to SCAN SCAN SCAN! you WANT 0*KR, 1-3 is decent anything over 5* is cause for worry/caution. KR is Knock Retard, or the *of timing the engine pulls to prevent detonation. Theres a TON of suff that can cause FLASE KR, you can usually tell false KR during a scan by how it shows up/when/and duration.
better read on KR
http://www.zzperformance.com/grand_prix/articles1.php?id=20
that being said, you can most likely drop to a 3.5" on the mods i recommended. a smaller pulley increase the speed @ which the rotors in the blower turn, forcing more air into the Lower Intake Manifold, creating more power. Dropping further sizes will require more mods ( ie headers/powerlogPEMS, bigger injectors, meth kit or intercooler, etc..)
In theory the more air the blower puches, the more power your car will make, there are other factors in that though
