I've got a 2000 Cavalier, 2200 OHV engine, I may be ordering exhaust parts fairly soon for it. I am thinking of getting the coated Pacesetter header, the Magnaflow 94035 high-flow cat, the Magnaflow 10425 resonator, and getting 2 1/14" pipe custom bent at a local shop. I'm keeping the muffler I have now, its a Hayame type 2 3" inlet, 5" (i think ) outlet. I want to keep this muffler because it has a nice deep non-raspy sound to it. I also plan to replace both O2 sensors with NTK parts, I may go ahead and get a heated one for the downpipe sensor, as I don't want to deal with closed-loop problems. Is there anything I should know, like would it be a good idea to cut the slip-fit connector off the header downpipe to reduce restriction if any, so on and so forth. I'd ask what sorta power I might gain from this, but I know that its nearly impossible to guestimate with any accuracy. I personally figure I might see 5-8 HP max gains, maybe more, maybe less, and probably mostly at the upper RPM range. If anyone knows something different, please let me know. Thanks again.

Some people will strongly disagree, some will agree, but I'd say if you're going to have a custom system bent, get 2 1/2" piping instead of 2 1/4". There are some with the opinion that 2 1/2" is too big but this just hasn't been proven by what we've really seen here (also, from my own experience with my ex's car, the 2 1/2" Megan Racing exhaust did nothing but add power, not a lot, but there was no loss of power in any range, that's for sure). The downpipe on the Pacesetter header is at least 2 1/2" (I think it may actually be 3" even), and the inlet to your muffler is 3", so if you go with all 2 1/2" components, you won't have any bottlenecks at all and it should be even more free flowing. Of course you'd need a 2 1/2" cat and resonator as well, but I would really suggest that route and not 2 1/4".

I was gonna say the same thing...2.5" downpipe to a 2.25" exhaust to a 3" muffler is a fair bit of turbulence. If anything, stick with 2.5" for your tubing and cat/resonator.

Also, Magnaflow converters were pricey, last I knew. Try the Dynomax Super Converter. I know Jegs sells it for around 52.99. NEVER had a problem with mine.