I'm familiar with the "take a run at the hill" syndrome but this slows down really fast, faster than other trucks I've driven. At close to 60+ heading up the grade, I'd be at 20 very shortly with no load other than my gut! This should be a torque monster (for the day) with the 261. I'm going to borrow a compression tester from a friend and see what I'm at per cylinder. Something just doesn't seem right.
Bruce