Mine fit perfectly, I had to "adjust" the heat shield a little to clear the rear O2 sensor. Both my cats are MUCH louder, but I had no resonators. I have since installed a glasspack in my GP which had chambered mufflers. It was NASTY sounding. My wife's Monte with magna flow mufflers and a custom 2.5" mandrel cat back was nice at first, but has developed a vibration inside at certain RPMs. It is also throwing a knock sensor CEL. I have ordered a dynomax race magnum 12" bullet muffler which should take care of these issues.