Magnaflow used my truck for their R&D work on their 4" system. Had my truck a week and gave me a rental car. In exchange they gave me a 4" system free. Here's my thoughts. My muffler is sitting in my garage next the the cat. The truck sounded like crap. It's almost like they took the muffler off their Honda kit and modified it to fit us with 4" openings. I was not impressed at all. I hated the way the truck sounded from the day I picked it up. Driving away from their R&D facility saying to my self, what did I do. Yes it's loud, but sounds really bad. I've since straight piped it, which I know is personal prefernce, but my temps went down 100º less muffler. Based on sound I would not recommend Magnaflow. Based on customer serivce, intallation and the price, good.