Hey if anyone can answer this question it would be much appreciated. I am getting a cat back exhaust installed on my GTP soon, and I wanted to get the resonator cut out and a Borla XR1 muffler installed in place of it and then run straight pipes back from there. I took it to a custom exhaust place and they said that the XR1 wouldnt fit because it is oval shapped instead of round. They sugjested that I have a Magnaflow muffler put in place of the resonator instead. I was wondering is Magnaflow as good as Borla? I have heard mixed things about Magnaflow before. I was also wondering if getting the U-bend taken out will make a big power differance? Thanks!