Seems like many folks are having luck killing the drone by adding an additional, small muffler, into the system.
I have a Magnaflow muffler & do, definately, have the drone, especially, when towing uphill in the 2200 rpm range. The sound FILLS the cab of the truck. However, it's not that often that I am in that situation.
Some people seem to be very sensitive to different sounds. I took my Duramax buddy for a 300 mile ride & by the time we got back, he had a headache & swore he would never ride in my truck again. I've driven it across country & had no problems. I even roll the windows down, with the radio off, just to listen to the exhaust note.
Joe F. (Buffalo)