[PaulE]

As a casual observer of these drone topic threads, it seems to me that the cheap eBay mufflers drone because one thing they all have in common is there is no cross-over pipe between the two mufflers. So there is a completely separate exhaust system for each cylinder bank and at a certain rpm the two separate exhaust streams create the drone. If you look at the Fabspeed maxflo muffler it has a cross-over pipe between the two mufflers and their latest edition also has a cross-over pipe in the exhaust tips too. The Fabspeed unit is a lot more money than the eBay ones, but perhaps adding a cross-over pipe between the two mufflers on an eBay unit would eliminate the drone.