2007 379 Peterbilt losing power help please

I have a 2007 379 Peterbilt 13 speed with an NSX motor in it had turbos checked out they are fine wastegate is good actuator is good I had a egg diagnostic ran on it diagnostic came back good set 1 incompatible file in the ECM software they put the correct software in it Peterbilt did this they checked my turbos make sure that there was no vibrations that was good everything I seem to do comes out good except for I'm climbing a 6% grade then if I hit it at the bottom of the hill at 70 a time I get to talk I'm doing 25 and overhaul or sorry overhead was just ran on it about 5000 miles ago I just did a inline or sorry in frame overhaul was Don Allen it around eight hundred and eighty thousand miles it now has 1.2 92182 miles on it I'm kind of at a loss don't know what to do. About doing a Dino on it it seems to be losing way too much power for what motor it is and the horsepower and torque rating any help would be great there's no white smoke coming out this tax to make me think it was anything to do with injectors by the fact I hardly ever see any smoke coming out of the sax like I said any help would be great thank you have a great day