[natmad]

It's all about TOTAL amount of restriction in the exhaust system.

Freeing up SOME of the restriction means a little less TOTAL backpressure.

A little less backpressure frees up a little bit of power.

This is how a catback frees up a little power, and this has been proven on dynos time and time again. Even a little gain is more than none. For me, it's all about the NPP sound anyway.

NPP valve closed is like a stock exhaust.

NPP valve open equals a very small catback-like gain in power.

This should be very simple to understand.

Edit: Gajagfan, congrats on getting your ride, how 'bout some pics?