[Nixon1]

I've read up on a long discussion on this stuff on my old board for my old car..ThirdGen.org... From what I've heard and thought up myself, here's my best guesses on this. Open headers is the best exhaust system. They've always got good diameter to them, and allow the exhaust gases to rapidly escape. Here's WHY an exhaust SYSTEM with too large diameter doesnt work good. What happens when air hits a pocket? It expands, obviously. When it expands, it becomes less dense. Denser air moves quicker. Thus, air in large tailpipes slows down...which also causes it to cool down more in the pipes. This creates an obstruction to additional airflow, thus by INCREASING your tailpipe diameter, by my estimation, you're actually INCREASING your backpressure as well!! So...open headers, you're good to go if you can get past the backfiring issues! Exhaust system..keep the diameter limited...2.5 seems to be the best for almost any car out there, whether it be V6 or V8. 3 in. is good for heavily modded cars...otherwise, I wouldn't try it..loss of bottom end torque is too bad to justify it.