I tried some different pipes for top end on my C6 and you can really tell the difference, but my lap times are always faster with a little less top end and a whole lot more bottom running a JP3 pipe. But the style of driving I think has a lot to do with it to, some run big open turns wide, sorta relaxed mono speed with little brakes, I run aggressive pipe to pipe on the corners the shortest way around the track and use lots of brakes with lots of speed changes.