97 7.3 exhaust drone?
 

I have a 96 f250 7.3 I just cut the cat and muffler, and developed a drone @ 1900 rpms. if I shift out of OD it goes away if I get to that rpm in OD it drones. what would be my best plan of attack to get rid of the drone? it is driving me insane. hollow out the cat and re install? thanks!

Install a 30-36" resonator.