It doesnt work that way though. When the pressure is negative on the outside as the air is being SUCKED through it would make no difference. Now if the pressure was positive it would aid in smoothing out turbulence....in say a boosted app. Diagram of how it works. In theory your saying if I put 4" tips on my 2 1/2 exhaust pipe it will flow better....? Same concept just in reverse.

 

If you ran 3in all the way out of the exhaust then it would run better than if you ran 2in...

Not catching your thinking here at all but why would so many people do it and then show gains? Those just imaginary horsepower that are coming in after the p&p and people are b.s.'n it??

 

People do report an increase in HP with a ported TB. I have heard of up to 10 HP.

Bill