So Greg Dupree says "...." and now it's as good as law. I would like to see a dyno difference between the two and I know that would be difficult with all mods being equal. I know that Greg knows a ton about Z's there's no doubting that. But I doubt that there would be a significant power difference between 2.5" & 3". I wrapped my 3" dp's with heat wrap to keep the exhaust gasses flowing and I will wrap my testpipes when they get here. Aside from that the only way you will convince me that the 2.5" dp's are better is if I saw a dyno run on the same car. If you are repeating something that someone else said please use " I think" or "in my opinion", because it really is just a theory.