I have the MAC axle-back on my '12 GT. Amazing sound. Absolutely the best sounding exhaust I have heard on a Coyote GT. But, the drone is quite intense at times. I don't mind drone much at all and at times it gets a bit annoying to me. I will never remove them, though. The sound is too awesome.
What speed and RPM are you hitting the drone? What gears you have? I'm often going around 69-74mph in the neighborhood of 1900rpms with my 3.15 gears. Any pictures of your exhaust? Rolled tips or no?
There, done interrogating you