exactly which borla muffler do people use as a presilencer?...

im thinking there most popular universal one...the xs pro muffler

Modefied 7, I need your e-mail address. I'll send video right away.

A cat will help. I bought my car with RB header/presilencer and Apexi N1's. I replaced the presilencer with a high flow cat and it killed some of the resonance. One high flow cat is probably not going to be much more restrictive than a what you have on there anyway but it will lower the pitch just enough.

Have you ever looked at a catalitic converter? Its a brick with holes inside of a metal case with pipes on the end. I'm sure its more restrictive than an RB silencer and likely the XR-1 muffler too.

It's a rotary engine..... get use to that weedwacker sound. The bigger your ports, the more its gonna sound like a cr250, or a weedwacker on meth.