Is anyone on here familiar with side branch resonators? I have been throwing around the idea of adding some to my 2001 GT that has BBK x-pipe and flowmaster 40s. I don't want to change the sound, just want to get rid of the 70-75 mph drone associated with the Flowmasters. Anyway I was reading about "side branch resonators" and found this Autolounge.net | Calculators | Exhaust Resonance and it says to add X amount of tubing to get rid of 2200 RPM drone. What about with the X pipe? is that still 4 cylinders per pipe, since it has a crossover? Thanks