F350 7.3 powerstroke lost power

[Old Chipper]

I have a 2000 F350 7.3L PSD, 45,000 miles, has been well taken care of. Started on a 2300-mile, trip pulling a 33 foot 5th wheel. On the 3rd day it started losing power on the big hills. Cruise set at 60, it would drop back to 40 or less, turbo going like mad. Stopped early, was told by a mechanic that, this was due to my driving with the cruise and Overdrive. Started out next morning (no cruise or overdrive used) ran good until late afternoon. Stopped to change drivers at about 3pm. From then on it wouldn’t go faster than 35mph, limped along to top of hill, got it up to 55 going down the other side, but couldn’t hold it up the next one. Dropped to about 8mph, engine was running very rough.
Had to be towed to the next town. (note; this was in WY and MT so these where good sized hills. Waiting to hear the bad news from Ford dealer! Was hoping some of you could give me an idea of what may have gone wrong. I had it serviced the day before the trip. All fluids changed, new hoses, tires, shocks, the works! I read that some of these had bad tanks, could that be the trouble?
Thanks

[jonmark1985]

Many times a power loss that happens that fast on a diesel is a plugged fuel filter.

[brettrw07]

you could possibly have a fuel pump going bad. i would check the pressure after the fuel filter and that would tell you if that was the problem being that you just had a service done on it the filter should of been changed.