From everything I've read for the V-6 mustangs spintech mufflers, bassani, borla, and magnaflow mufflers are the best. Flowmasters sound good down below 3000rpm but the sound tends to thin out any higher than that. Bassani, borla, and magnaflow are farely quite at idle but get louder and more aggresive as RPM's increase. And spintech's seam to sound good through out the RPM range. Another benefit to Bassani, borla, and magnaflow is that they're stainless steel, so they won't rust out.