Fuel mileage still sucks

[SquareOne]

Do you have a boost or pyro gauge? It would be nice to know what the boost psi is under load and while maintaining speed.
With 78k, sounds like you're pushing it pretty hard getting to get to speed. The rpm you're running it up to is a good habit to have though.

The norm around here for guys trying to get the best mpg is to keep the boost at 10lb and lower whenever possible. The pyro will typically tell the story as well. The more fuel, the more heat you'll create. The less the heat the easier you're being on the truck which should translate to better MPG.

When was the last time the doser injector was checked/changed?