Originally Posted by projectRDM

What a whole thread of fail.

Backpressure is something some fool made up 60 years ago and people still swear by it. An engine does NOT need backpressure, period. You want to get all the exhaust air out as quick as possible to avoid creating backpressure, which chokes down the engine. A very small amount of lowend torque is lost due to the added flow, but it's hardly noticeable even on paper. There has been TONS of dyno graphs shown for nearly 20 years proving that the bigger the exhaust you have on a KA, the more power you make. Done.