There's only 2 reasons not to buy a used exhaust. First one is damage that might cause an exhaust leak, the second is if its seen a lot of miles and any of the components use fiber packed mufflers. An exhaust that uses a degradable filling in the mufflers/resonators such as the AAM exhaust (Vibrant) will lose its noise dampening ability with use.

 

Good point helldorado - how'd you find out about the AAM filling material - that's some good detective work there!

 

I know they use Vibrant mufflers and resonators and Vibrant is glass packed straight through perf cores. Great performance and I think they have an awesome sound, but they degrade over a 4-5 year period depending on use, so its something to look out for on a used exhaust.

If its not a chambered muffler, its generally straight through and the outer chamber is filled with some sort of dampening filler, and they all break down and lose effectiveness over time.

 

I also wouldn't buy a used knockoff - for the reasons stated above about the poor quality of materials/ workmanship.