I have got a 2011 6.0 gas GMC sierra Dually
I've installed 1 7/8 long tubes plus a magna flow muffler but the sound of the truck did not change much but the drone is just annoying could some one advise me about increasing the sound abit and how to eliminate the drone ?
Thank you

 

Add a resonator to remove the drone.

 

I did a resonator tube, per the sticky at the top of this forum section. It killed the drone and quieted the exhaust a bit. If you are wanting it to sound "meaner", you may need to swap mufflers. I would do that before doing the resonator tube, as you may need a different length tube after swapping mufflers.