Like every one says check the fuel pressure. When you replaced the fuel filter (cannister type not the spin on)did you look into the cannister and see if it was full of metal? Make sure to clean it out. If you can check the psi at the shrader valve or top of the filter head, hold it to the floor and keep a eye on the pressure,if it stays constant and the truck starts smoking and logging check engine lights (Cummins code 368) it's the pump. If you see the pressure dropping off check for fuel restrictions or air.