And while we are on the subject: A PDF with some info on how to make power out of your exhaust system. These are just things that exhaust fabricators think about all the time. Most people don't realize the science behind building headers or an exhaust system but this will help show what kind brain work goes into a proper system.
Headers, tube size, collectors, X-pipes and more exhaust technology summed up in a brief article here in this
exhaust system PDF.