I had the Ford Racing axleback sport exhaust on a 2012 GT and it both sounded great and had no drone. But the Ford Racing axleback sport exhaust for 2015 Mustang GT's is built by Borla, and my experience with Borla mufflers on a Corvette was that they had a terrible drone between 55 and 65 mph. Do the new Borla-built Ford Racing axleback mufflers for 2015 have a drone, or are they relatively quiet inside the passenger compartment?
We have only tested a few different set ups on our company cars. This one we have not tested, usually on the FRPP units they do not experience drone around 2K. This being an axle back rather than a cat back you would be less likely to experience it as well.