just got doe with the 6.4 classes , do not see any reason why a cat back system wil harm anything , yes they say the motor monitors all exhaust pressures ,but nothing is monitored after the diesel particulate filter which is a self cleaning system and is after the catalytic converter so my guess is elimination of the muffler wil probably be ok no other mods wil be able to be done , just for the record the tail pipe is designed to help cool the exhaust coming out down because when the computer does do a regeneraion in the exhaust it gets to major high temps and wil brn the paint, ive already heard of one catching the grass on fire when a manual regeneration was done