Agree on the 3800-4000 rpm resonance (and really depends on the gear), which has increased with age as exhaust/fiberglass in mufflers has worn in (I have about 15k miles on the exhaust). However, I would not characterize it as an annoying drone, but more resonance/harmonic like....actually think it sounds really awesome and can't be replicated by any exhaust I've heard so far...I've gotten numerous random compliments on it, even though M3s are a dime-a-dozen in CA. Despite offering no HP increase, other than a tune this has been my favorite aftermarket mod.
Originally Posted by Gearhead999s
Mine does the same thing in the 4000 rpm range when the exhaust is hot.I think it is a normal thing as the exhaust note outside the car also changes so it is not an issue with mounting or loose parts in the exhaust itself.I really do like the different tones that this exhaust gives off at different RPM & temps.And I really like the fact that there are no annoying drones in normal day to day use and long distance highway driving.