Low torque cm2250

[Scooby d]

Truck is a 2012 cm 2250 with 430k miles. Overhauled at 350k miles because of carbon packing behind the rings and top of liners. ( old style liners without carbon rings ). Truck is worked hard as a heavy haul truck but gets lots of pto time. I have felt like the truck has been under powered since I bought it (125k). Torque gauge only goes to 80 percent. Took it to pete shop 2 weeks ago ( first time ever and never again) for latest ecm updates. I'm wondering if someone could help me out on low power issues and then I'm going to fix it so my oil stays cleaner. I've never been to a shop with it before and not only did I get ripped off but I learned that my jake brake was electric and had nothing to do with oil or oil pressure. Lol ... vg ring is free, turbo is good, no air leaks, runs smooth with no codes, fuel pressure holds good, new injectors changed nothing. It feels like the truck is derated but no codes. I have insite but Don't know what to look for if it has a ecm derate. Could the company that owned it before me derate it somehow?