Originally Posted by Jordan Y.

An engine doesn't need backpressure to run. That's a very old misconception. Backpressure is just a restriction on getting the exhaust out of the cylinder efficiently. What an engine needs is a properly sized primary exhaust tube off the port to keep flow up and help scavenge the cylinder without restricting flow at higher rpm.

Also, lots of guys running NA run open header without any problems other than loud noise. Black Venom ran his LT1 Firebird open header for a few hours just to try it out and the cutout we welded into the exhaust was right after the Y.