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Replacing Catalytic Convertor with a downpipe, suggestions on where to get it?

A

aeidian

New member
99 Grand Prix GTP 3.8 Supercharged

Resonator blew out on my stock system, so I removed it and the cat. Cut the down pipe right before the cat and left the stock down pipe on there, ran straight pipe through the section I'd cut out. I didn't realize that I had an exhaust leak coming from the down pipe bracket that bolts to the exhaust manifold when I did it. I figured that it just didn't seal completely when I put the straight pipes on. I planned to replace the cat and the resonator shortly, so I just ignored it. The down pipe broke completely off the bracket that attaches to the exhaust manifold so now it's time to yank it and replace it. I've toyed with the idea of putting a Magnaflow direct fit cat back on, but I'm not crazy about paying the $185 for it. I've read a couple places that I can just put an aftermarket down pipe in place, and it seems to be cheaper than getting a cat, since it's just a pipe. Question is where do I find this? Obviously Orielly or Autozone don't sell this since it's not street legal, so where to and how much? Someone in another thread mentioned ZZP, and I found this link:
ZZ Performance

It lists there for $89 which is fine, but they have options that tick the price up and I don't know what size I'm looking for, anyone know? Everything is stock on it. I'm just looking for a cheap alternative to replacing the cat right now, and don't care to spend as much to get a downpipe as I would to get a direct fit cat, so if anyone has suggestions of a site that sells a cheaper down pipe, please let me know, thanks.
 


you want a bolt-in 3" w/cat. unless you dont even plan on modding the car even the slightest bit, then you can get away with a 2.5" downpipe.
 
I don't plan to mod it at all. I don't plan to put a cat back on there, not for modding reasons or any other reason other than saving a few bucks. So I can put a 2.5" down pipe on there and it'll bolt right up? If that's the case, it looks like that site will offer it for 120 plus whatever shipping will be, which seems pretty close to the 180 I'd pay to get a direct fit cat from a local parts store, anyone have any other site suggestions for a 2.5" down pipe?
 
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Think I've found a 3" catless. What size is the pipe before the Y? Is it 2.25 or 2.5? I'll need to get a reducer from 3" to whatever the pipe is before the Y. I had problems with this before and had to use a hell of alot of reducers, but I'm pretty sure I can find something online if I know what size it is.
 


before the y pipe the catback is 2.25". if you get a bolt in pipe, it will bolt right in to stock everything and use no reducers.
 
Looks like the 3" I"m getting goes to a 2.5 at the end with no flange. I'm just going to run straight pipe off the end, so I'll get a 2.5 to 2.25 reducer, right?
 
Wait...did you not just buy the 3" bolt-in? That'll bolt up to your stock catback with no need for a reducer.
 
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