yeah, keeping heat in the pipes. I've also heard some thing to that effect as well. I just don't know how true it is. I mean, open headers do not keep heat any farther than the collectors length and some car run hard like that and some run great with complete exhaust systems. The aluminum tubes that I intend on using now are thicker than the stainless 304 tubing that I have been using for the sake of not distorting out of shape and keeping the sound to a minimum. I think that exhaust tube/muffler thickness experimental sessions at the factory have to do with sound retention. I could be wrong. If anyone on here has another opinion, then feel free to cut up my theory. LOL.

I remember running Straightline Performance Titanuim bullets that were super light and super thin and were quite noisy for the street, then I I purchased the Dynomax Ultra flows and the noise went down substantially.