Lack of power up hill loaded or empty

[Peterbilt]

2006 peterbilt 1.5 on body 400,000 on rebuild 355 rears I think, 30-32 o on boost in a hard pull,no coolant consumption about 1gallon of oil consumption between oil changes . Every 12,000 miles cac has been checked . New turbo,new actuator . Intake sensor changed along with temp ,fuel pump in the last 30 days. Don’t remember if the delta -p sensor has been changed.13 speed trans.I have not found someone with insight to do injector test.also new egr valve and sensor . New to the Cummins engine . Been a Detroit man . Thanks for your info