I'm wondering if there is a simple cause-and-effect guide to exhaust modification... like "a longer header will..., shorter will..., wider, size of expansion chamber, etc." I have seen simple explanations for other modifications like gearing or porting, I was thinking about putting together an experimental exhaust and most of the stuff I've read is waaaay to cerebral. I just want to know what effects top end, low end, rpm, etc.