[blue00gt]

It's debatable what muffler is 'the best'. Any good straight through muffler design will make more horsepower than a flowmaster on a stang, although it's only a couple of horsepower difference unless we are talking about a racecar. It all comes down to what sound you like. I personally don't like the low-mid-rpm interior drone that you get with a chambered muffler like the flowmaster. On my '79 Pace Car with the American Thunder catback, it seems to be loudest inside at exactly my freeway cruising rpms, and it actually has given me a headache before on a long drive