A 'real' pro circuit T-4 will make a big difference, as will any of the good aftermarket pipes. You'll be dropping some more coin to get one than what they want on ebay though. As for ebay copies I dunno how they will perform. If they have copied the originals closely they could give some advantage purely in increased diameter, but nowhere near what the original will do. See, the good pipes cost so much because apart from all the testing they do to find the ideal length and diameter for best power, the pipes are made from mandrel bent thinwall tubing in either stainless or titanium. What this means is that at the bends the diameter remains the same and the pipe is as light as possible yet strong. Now go out and have a look at the bends on your stock pipe which is done with a pipe bender. Those restrictions at the bends completely choke your stock pipe and are very upsetting to the rebounding and outgoing pressure wave in your exhaust. I guarantee you those cheap pipes are all done with with a bender. They are chrome plated mild steel same as your stocker and will only give a bit like i said if they happen to be a bit wider.
