I have a 1998 Ram with a Cummins 5.9 . It’s been running Greta up until a month or so ago. It seems as if the peddle is no longer usable past about half throttle. The truck will not go past 45 on the highway. I have changed the fuel and air filters and no improvement. I am stumped as to what this could be. Any advice would be great. Thank You, Al

 

12 valve or 24 valve? If later, try go pedal calibration, like here; https://www.cumminsforum.com/threads/apps-reset.1107/