Hi, Eloy,
Check your oil level. If the truck seems to be manufacturing oil, then you have a leaking injector, which would also account for a "miss," regardless of what your dealer says. Don't mess around if this is the case. Shut it down, and get thee to the dealer. Ask to have a "kill" test performed, and if they look at you funny, try to get it to the Cummins shop for this. They don't need the factory's programming of the ECM to diagnose a bad injector.
Good luck!