My recently purchased '01 has an aftermarket cat of some manufacture. Don't know which! The install isn't ideal but after changing the saddle clamps I've eliminated a leak at that connection. There seems to be a "leak" in the converter body on the top that I can "feel" with my hand when the tail pipes are "stuffed"! The post cat 02 was also a "cut & splice" of sorts and I've replaced that with an OE GM piece!

I get random P0420 "converter performance" codes every couple days.

I don't mind the buy of another cat but I'd like to buy a "proven" performer! I'd like not to have to program the P0420 out of the PCM and I don't want to have to be concerned with "post cat" 02 location.

Suggestions?

Another question! Has anyone eliminated the resonator near the cat? I run Corsa exhaust on my Corvette ZR-1 and I'm interested in maybe "spiffing up" the exhaust rumble! I'd like to avoid "resonance" in the cabin!

a member here used a Goerlich (i think thats how its spelled) cat, it didn't set the SES light

goerlich 608227 3" in/out

Yep thats the one. Purplehaizer swears by it.

That'* the car you want, others will trip a SES light, as you already found out.

Removing the res can make your car sound raspy. Some times cars sound ok, but other times, not so much.

Anything you do that changes flow will change the sound. Rockers or cam will deepen the sound, a Plog or better yet, headers really changes the tone. A lot of members use the flowmaster or magnaflow series 80 muffler, or series 40 if you have duel mufflers. Changing the size of the pipes isn't worth the cost or effort, you have a 2.5" exhaust, leave that part alone. The bigger cat is worth it though, get the 3"

OK, AP & Goerlich are one in the same now and the 608227 looks promising but I can't seem to find a jobber that does AP/Goerlich locally. I'd like to make sure I buy a cat "THAT HAS" an O2 bung in it to be used for the "post cat" location! I'm not convinced but with the cat that'* on the car the post O2 is in the original location several inches beyond the converter body!

I'm also interested in buying a second exhaust system from an '01 to experiment with modifications. I believe I'd like to remove the resonator and place a 3" in muffler in the intermediate pipe vicinity and use 2 1/2" pipe to the bumper with some sort of an exhaust tip package. I've got a set of Corsa tips, a pair of 3" tips from an SS Trailblazer, a pair of GM dual-tip pipes for the '04 up GP and of course the "cow-bells"!

To be practical the exhaust system would need to be in or near the Washington DC area. Anybody got anything?