i have a 1998 gsr db.. and my cat now is going to all sorts of hell.. i removed all of the heatshield b/c of prior noise.. but now i think the cat has just gone bad perhaps from age and high rev straining.. anyhow, i am thinking about a full exhaust changeover? actually maybe just a new cat or something?

i know that my car has 2 oxy sensors.. i think one in the header and one in the cat? so what do i do? i dont want much trouble.. just no more noise...

what im asking is where to get a cat i suppose? i am also considering a apexi ws2 catback.

 

I dont belive any cat back exhausts come with cats, high flow cats or test pipes. A cat back exhaust will bolt up to the cat and go all the way back. You can get a test pipe(straight thru pipe) from like ebay if you search test pipes, testpipes.com, or you can go down to your local muffler shop and have it done. A test pipe will fail emissions though. You can probably get a cat from your local dealer or get a high flow cat.

 

Buy a high flow cat. I recommend a carsound / magnaflow cat. They flow better than pretty much any other cat on the market.They're universal but pretty much any muffler shop will weld the flanges on.

You should probably get at least 2.25 inch piping from the cat back if not 60mm (2.38 inch) or 2.5. The bigger the diameter, the more air flow. Whatever you do, don't get a cat that's bigger than the exhaust piping (say a 2.5 inch cat to 2.25 inch pipe). You want the diameter to go from small to big OR stay the same the whole way (2.5 collector / cat / exhaust)

What i did was run an aftermarket header (comptech) with a 2 inch collector (stock size), to a 2.25 inch carsound cat, to 60mm Tanabe cat back. So the diameter is increasing the whole way out.