We are heading into the colder seasons of the the year. Does your vehicle's Drone noise change with air temperature?
I have been toying with the idea that the RPM and throttle setting where drone occurs could be shifted by injecting air into the exhaust with a 12 volt compressor. Water injection might work also.
Cooler exhaust gas should have a lower speed of sound, which should shift the conditions where the Drone is loudest.
Someone adventurous might also experiment with adding E85 to the fuel.