suby01 wrote:u can aways go custom, find a muffler shop, get some sweet mufflers offline ebay w.e and get someone to make you a catback or even straight pipes. shouldnt be more than a few hundred for that. if i were to get one on my G i propably would go that way.
But if one is looking to actually gain performance or at least not lose any, this may not be a good idea. Many exhausts developed for the G and Z actually lost power. Stillen went through several versions for the early coupes and the 350Z before they finally designed one that made good power. Other brands released versions that made small gains or even lost power. What you pay for is not just the materials that go into manufacturing the product, but the R&D to make a good product.
If one insists on going the custom route though, I'd recommend at least trying to mimic an exhaust that is known to perform well. And use quality parts. There are plenty of good mufflers to choose from. Though, by the time you pay to have someone cut up a bunch of mandrel bends and weld them into an exhaust system, the cost may start approaching the cost of a good prefabbed system.