Because it is in a PacCar chassis, PacCar will basically do nothing. If you would like it back to original, take it to a Freightliner dealer. Yes you read that correctly-Freightliner dealer. Most diagnostic/tuning equipment that's independent won't correct issue. Freightliner will reprogram according to engine serial number through Daimler. If you want it turned up it can only be done with accordance of Freightliner and most likely 500 hp @ 1575 torque will be max. * A real tune-up, only consists of adjusting valves, injectors and jakes. What people are referring to as a {tune-tune-up} is trying to do a bypass to more horsepower. A real horsepower/torque change is called a rerate by manufactures/dealers.