Installed M&S 3" Downpipe
On 9/12/2004, I installed my M&S 3" downpipe with hi-flow cat converter. The upper bolts were a little tricky to get, but once I got the leverage and the correct combination of ratchet and extensions, the old downpipe was off. I test fitted the new downpipe and found that the flex piece in it was hitting the floor pan of the car. After a little persuasion with a 5-pound hammer, I had enough clearance and installed it with new front and rear gaskets. I also replaced the rear bolts where it bolts up to my GMPP Cat-back exhaust with Stainless Steel hardware.
After I installed it, I fired up the car and let it warm up. The exhaust smelled a little funny, but that's normal with new piping. Once the car was warmed up, I revved the car and noticed that it revved much more freely. The exhaust got a little louder and a tiny bit more raspy, but after taking it for a ride, I realized that the pluses were worth more than the minuses.
Here is a picture of the stock downpipe (left) next to the M&S downpipe (right).
What you can't see is that the stock downpipe is double-walled piping in the piping before the cat which causes a good amount of restriction. Tests have shown that installing a 3" downpipe can give you up to 8whp over the stock. This mod also helps get rid of Knock Retard which is always good.