My set up works great for me, but maybe not for others. There are a lot of variables. 2.5" collectors with 2.5" pipe welded to the 2.5" flange (at the proper angle) into duel Walker Turbos (not sure why no one ever mentions them) with the outlets before the rear tires (only one bend after the headers) to reduce back pressure. The bends and lengths are all the same on both sides. The headers tubes should all be the same lengths also (a good set). I agree with others here, stick with the 2.5" and you can still grow on your HP if needed.