Suggestions for muscle car sound muffler without drone

A crossover may have helped. The Dynomax VT's helped to lower the level of the drone 12db but the branch resonator totally eliminated the drone frequency. I've read of cars with crossover pipes droning. There seems to be a number of factors that can affect drone. Apparantly from what I have read it boils down to if the engine and exhuast system create a frequency that is at the resonate frequency of the tail pipes that act like a pipes on a pipe organ.