I can tell you.. it makes a difference. I had 2 1/4" exhaust with the STOCK resonator welded on (at the time) with the turbo. I cut out the resonator and welded on a 2 1/4" pipe in it's place and I got more power I can tell you for sure. I also have an exhaust cut-out - it's ghetto, but it works.

The spool time was a lot quicker and I had more power all the way up to redline.