I was getting some pretty bad drone from my dual exhaust between 1700 and 2000 rpm. My wife finally complained enough I decided to do something about it.Did some research and found 1/4 wave branch resonators. It's just another piece of exhaust pipe that branches off your existing exhaust pipe or pipes at 90 degrees of the exhaust flow and is capped on the end. To get the right length you'll need to figure the wavelength of the sound at the rpm when the droning occurs, divide that by 4 and that's your length. the formula is pretty easy to find if you google 1/4 wave branch resonator. It worked beautifully though. It eliminated all the drone. Really cheap and easy to do too.