Ok, thanks to all those with the helpful replies.
I'll try to answer your questions.
1. Mileage was hand calculated and compared to my dash mpg, was within a tenth or two.
2.Havent noticed any more black smoke then usual.
3.I believe my rpms at 65mph is around 1600-1800.
4.A stuck brake crossed my mind, I never checked for heat on the hubs when I stopped but I did walk around the trailer for a visual check each time I stopped and didnt smell anything hot or burning brakes.
5.Defintely going to have the injector balance rates checked too.
6.Im guessing my trailer is 11' tall.
7.Not sure what my unload mpgs are lately because I hardly drive this truck anymore, just used to pull camper/haul things.
Im no stranger to figuring mpgs, Ive done it weekly for years on my daily drivers.
I know my truck well, this condition is not normal.
