Magnaflow, The Flowmasters have restrictive piping as the Magnaflow is like straight through. Flowmaster uses the restriction to make a certain tone. If you look at a cutout of Flowmaster they have a some V shaped baffles in there to make that certain flowmaster tone, which will then cause some turbulence in there. Magnaflow has a straight through design, but still has a nice tone, i use Magnaflow. If you ever go F/I it will make a pretty big difference.