Cat C12 power issue

I know this question has been asked before, but I really need some help. I have a 2001 Peterbilt 357 triaxle dump truck with a Cat C12 2Ks motor 395 HP. I’m having issues on hill either loaded or unloaded. I lose power.

The following has been done, changed the fuel filters twice, installed a FASS fuel system, updated the pressure valve and spring in the secondary fuel filter housing, adjusted the valves, two of the six injectors where out of alignment, changed the air filter. CAT Tech hooked up the laptop, engine is a 395 HP and said he wouldn’t recommend turning it up since I would lose torque. All the sensors are working, under a load the fuel pressure and boost drop, then recover.

I’m considering changing the fuel pump since there is another pressure valve in it, there have been 6 updates since 2001 and I don’t think one has been done. The turbo and wastegate appear to be working just fine. No play in the shaft but there appears to be one fin slightly damaged. I was thinking of going with a PDI stage 1 turbo.

Several other trucks that I run with have the same engine, and they fly by pulling a hill.

Any advice