VA Beach/Hampton Roads

Tigger

Meh. You'll always get rasp from test pipes. It's well documented throughout this forum. You need HFCs if you want the rasp nearly gone. RTPs aren't enough.

The answer to your question as to "why." I'll let someone that knows that specific answer tell you but we all know they do it and that's typically enough.

Btw, RHFCs are the best for an NA car where you absolutely want zero rasp but still want the best flow along with the benefits of keeping your torque figures. TPs on this car result in a net loss of low end power. You need that back pressure for something!