Turbo Pro Muffler - Optimal Flow, No Drone, No Resonance

I have to be honest here. I had my local muffler shop install your Turbo Pro Mufflers on my 340 Duster, and while the exhust note at the rear of the car is "slightly" lower in volumn and pitch than it was with my Magaflows, the drone noise I was hoping to get rid of while driving is actually a bit worse, albeit at a slightly lower rpm range. I'm tempted to put my old mufflers back on.