Originally Posted by synolimit

Just a question for you about the exhaust hiss. I just installed long tube headers so the hiss is a lot louder now and I can hear it while driving. The sound makes me think about the Subaru air pumps. See on a subi they have a air pump that turns on electronically and it is piped into the back of the heads. There are two electronic valves for each side on the heads that open and close so exhaust fumes don't come back out and burn the plastic piping. The point of it is to pump fresh air into the exhaust system to keep emissions down. See if they run the car richer it pollutes, but if you pump fresh air in you dilute the gas. While looking at a pic of an engine build, our heads seem to have the same exhaust ports on the heads. On the subis everyone pulls everything out of the car, buys block off plates and turns off the cels. It just loses weight and cleans up the engine bay. Can anyone confirm or deny this theory? It's the holes with the bolts and black gaskets.