can someone explain the need or lack of need for back pressure on a normially aspirated engine. i have heard all kinds of stories, like with no b/c you will burn your valves and such of the like. now i know this holds true in the reverse effect with the isuzu 2.6, to much and it burns valves. anyway can anyone tell me what the real deal is, and if you have facts to back it up post those also. id appreciate it.