Magnaflow vs. Flowmaster: Attempting to Settle the Eternal Muffler Debate. If you’re asking which muffler is best, we have answers, but you’re asking the wrong question.

The debate still rages over whether a Magnaflow or a Flowmaster muffler is best. We dig deep into the question and get some help from Engine Masters $40 Muffler Dyno Test.

You can see the power ratings below for each muffler setup below: Note, this testing was done on the 3-inch exhaust system. Magnaflow mufflers: 399.9 lb-ft @ 3,800 rpm / 344.2 hp @ 5,000 rpm; ...

Flowmaster does entire exhaust systems for all Mustangs except the '74-'78 Mustang II. This means complete systems for '65-'73 classics, '79-'04 Fox-bodies, and '05-'09 cars.