On my 07 5.9 mega after the muffler there is something else, a resonator maybe? does anyone know for sure, it is integrated into the bend above the rear axle and looks like I will have to replace the whole section of pipe if it impedes flow too much. Any knowledge would be helpful.

 

That is a resonator.. Only the megas got them from the factory. I dont think it impeeds flow at all though. A lot of guys do the muff delete on there megas and leave the res. I here it sounds pretty good.. Kinda makes me wish dodge had put a res on the quadcabs too..