You wouldn't get a thing. You would still have the same amount of backpressure in the pipe.

I have Tanabe Race Medallion muffler, custom 2 1/2 inch pipe to cat. High flow straight through cat. ( Basically a cherry bomb muffler) Thats where I stopped in hopes of dropping an h22 in soon.

To just mod your stock exhaust. You can cut off the resonator and weld in a straight pipe.