Drone seems to be at least partly about the length and size of the muffler and location in the system. The shorter turbo style mufflers I was using had a drone at certain rpms. Definately annoying. Using magnaflows now. Its a little bit apples to oranges though since the car is back to headers and H pipe location based on pipemax. Never been a Flowmaster fan - so that biases me. LOL. Pick the series carefully if you go that route!