I can get a 3" downpipe and have it installed (parts and labor for $45) when I get my new tips installed. Is it going to be worth it with my level of mods? Am I going to need an o2 spoof? Keeping stock cat, so I'm assuming no spoof is needed yet.
Also, will I see much more power?
Thanks in advance,
Martin

Anybody??

Unless you're going 3" full exhaust (I don't recommend it unless you mod like Rogue or Scott Cook), no.

how would it help if the rest of your exhaust is still the stock size?

If you keep the stock Cat you won't need a spoof.
You may benefit slightly with the supercharged engine if you replace the downpipe including the flex connector because the stock one is only 2" dia. and any decrease in restriction will add power. My guess is about 2 - 4 hp.

You're not removing the cat so no spoof is needed. I don't know why you would need a 3" downpipe, but it would probably free up a few horsepower, as long as you leave the rest of the exhaust stock behind it. If you open up the whole exhaust to 3" you will lose WAY too much backpressure.

If that doesn't convince you maybe this will:

My dads GTP (the one in my sig) runs 12.2'* @ 115mph...it has a 2.25" borla exhaust on it. Yeah, it has headers and a 3" downpipe, but the downpipe then reduces from 3" to 2.5", which then reduces to 2.25" where the exhaust bolts on. Having the big downpipe but keeping the small exhaust frees up any restrictions before the cat-back to give as much power as possible, but keeps the backpressure higher due to the smaller exhaust. The GTP pulled 315.6whp with the 2.25" exhaust on. I can pretty much guaruntee you that if it had a 3" exhuast it would have less power. With open downpipe it pulled 304.9whp. So basically, don't go too big, afterall, it is still a 6 cylinder.

Shawn

Keeping a 3" pipe between the headers and a smaller exhaust may work like a venturi setup.

I'm not sure the money and effort would be worth the minimal gain, unless you're modded out already, and that'* the last thing left undone.

if you can get it done for cheap great, but maybe you should wait to get a few more mods that will make more of a difference.

Right now I have no exhuast resonator, and have replaced the muffler with a Magnaflow Wide Open (3" inlet >> dual 2.5" outlets). Otherwise it is still the stock cat and piping.

I'm thinking for $45 I'll be the guinea pig. It may not be all that much power, but $45 for a 3" DP including install is alot less than what some of our 3800 perf vendors are charging.