Ok, I currently have an 01 powerstroke that I just purchased from a guy in st. louis and it has a banks 4 inch exhaust on it. I had an 07 cummins with a 5 inch turbo back magnaflow exhaust on it. I absolutely loved the exhaust and the sound of it. Now, ive noticed that often you see a 5 inch turbo back exhaust on cummins, but not powerstrokes. Guys usually have a 4 inch. Y is that? Does it not have the same effect on the powerstroke or what?