Just a heads up. The Power Wagon is NOT the ultimate tow vehicle. The payload is significantly reduced for that particular model compared to a standard 2500.
I tow a 2018 4x4 with the 6.4L, 6 speed, and 3.73 rear end. I am pulling about 8000-8500 and it tows great. I would expect it to rev up when in the mountains because that is what it is designed to do. Mileage is about 8 towing and 13 without, but I have a heavy foot. I do not keep vehicles long so I would NEVER recoup the cost of the diesel. I am very happy with mine FWIW.