I've still got the dmf, well it's the second one, and it's holding up ok. I don't run the piss out of it because I don't want ot have to buy a new clutch, but it's not too bad.
What's the best exhaust to use and maintain a stock sound in the cab. I've run a straight pipe for a while, but I'm not sure I want all that noise on another truck.
You don't lose bottom end, that is a myth. I like my 5" but there is no real advantage. I don't want to hear the 'backpressure' argument to the 5". The turbo itself is plenty of backpressure.