naturist wrote:
I know nothing of that particular rig, but I would point out that unless the engine is turbocharged, you lose a lot of power at altitude. I know that stretch of road goes from 5,000 feet to 11,000 feet, and non-turbo vehicles suffer greatly at those altitudes. That is one reason there are so many diesel recommendations here; diesels are almost always turbocharged and suffer no loss of power at altitude.
That loss is roughly 3 percent for every 1,000' of elevation.  Do the math... at 8,000' you have lost 24 percent of your flatland HP.  As noted turbocharged engines are immune but for most of us its can be a significant challenge out here in the west.
There are lots of gremlins that could be hurting the rigs performance from clogged fuel and/or air filters to simply needing a tuneup.  You should expect better performance than that. Good luck.
:C