I have a 91 LS and when I bought it it had a loud factory exhaust, there’s a loud buzz coming from underneath, sounds like it’s near the catalytic converter. I haven’t checked it out but I think the whole exhaust is about rusted out, one of the exhaust tips has rusted off already. I’m wanting to get a Greddy cat-back system but I was wanting to make sure that the general opinion on here is to use an OEM cat with the Greddy or it will sound bad. I’m thinking I’ll have to buy a new cat so I want to make sure and get the right thing. Also, does anyone know a good place to get a Greddy system? The cheapest I’ve found is www.wholesalehyperformance.com
Or would I be doing better to get a muffler I like and get a exhaust place to do the rest? Any help would be appreciated.
the Greddy MX is pretty good not sure tha tiw ould fix your problem you would prolly have to get undre the car to do that…but you could prolly get a new cat for like 50$ if you dont’go to the dealership…:shrug: good luck 
i have the RS*R exhaust system really good quality! i would recomend that! but i dont know what the cuzzing noise might be?
If you can get the front of your car up on jackstands and have someone else rev it, you can feel near the front and rear flanges of the cat to see if you feel an exhaust leek at either (Front is more likely unless there is an obvious hole). If this is the problem, you might be able to get away with just replacing ht e gasket. By the way, I have a Thermal exhaust and it is awesome.
i had a buzzing sound you could hear at idle and it came from a hole in the b-pipe. stock muffler is crap, had mine replaced 3 times till i bought a stainless. i dont think greddy is full stainless, id look for a thermal or tanabe super. you could try custom but make sure itll be mandrel bent.
I had a buzzing problem which gradually got worse. I fixed it by going under my car and discovering that the brakets holding the pipe in place had rusted and bork causing a rattleing sound that was really loud. simply buy some metal clips and fasten the pipe back into place tightly. working great for me although I still want to buy an exhaust system. GL.
Thanks for the help everybody. I’m kind of leaning toward getting a muffler I like and possibly a high flow cat and letting a muffler shop do the rest. Can anyone give me a ballpark estimate of what a decent price for getting a new cat and muffler installed as well as a mandrel bent exhaust? Also, would getting a muffler shop to mandrel bend me an exhaust be just as good as an aftermarket cat-back system?
Just thought I’d let anyone else with the same problem know what I did. I took my car to an exhaust shop and they said that everything from the catalytic converter back was bad. So they custom made a 2 and 1/4 inch exhaust for me with a high flow muffler and tip. It sounds great, has a nice throaty sound but is hardly noticable at highway speeds. Only cost me $150.00 labor and all. Very pleased! 
Originally posted by Gekko
Just thought I’d let anyone else with the same problem know what I did. I took my car to an exhaust shop and they said that everything from the catalytic converter back was bad. So they custom made a 2 and 1/4 inch exhaust for me with a high flow muffler and tip. It sounds great, has a nice throaty sound but is hardly noticable at highway speeds. Only cost me $150.00 labor and all. Very pleased!
What exhaust shop did that for you?
Originally posted by bbb
i dont think greddy is full stainless, id look for a thermal or tanabe super.
Yes, GReddy is stainless.
Greddy is only stainless muffler and tip - the rest is mild steel.
The exhaust shop is Shaffer’s Muffler and Automotive. It’s a local place. They’re kind of the exhaust specialist in town so I went there. Also a friend of mine got a good deal on a muffler for his 93 Legend from them. I’d recommend a local place if any of you are looking at getting exhaust. I’ve got great sound and I can tell it flows allot better.