This is a "fatal 4 way" matchup with no time limit. The argument will go on and on till the end of time. Anyone with dyno results, charts, professional opinions, or anything to say about either of these systems please chime in. My opinion is that I didn't care for the Magnaflow sound on my 2001 GT. I thought it sounded a bit too "old Chevy with glasspacks". I love the sound of Flowmasters, but I have read more than once on a few different forums that they do little or nothing as far as performance. Maybe the performance gain on the '03 Cobra is just because of a freer exhaust system, and not anything Flowmaster did especially for the Cobra per se? Lets stir the pot boys, and let the opinions start flowing. A little debate never hurt anyone.