Well Jesse, that sux. I would say that when ever you are getting that poor of milage, it is injectors or something else. I had bank one go down 20% a couple of weeks ago, and my milage droped to around 12mpg. So if you have a couple injectors messing up, or leaking, you could be getting less. How far do you drive to work, is it in town, short trips, or longer ones. I am sure you have been pluggin your truck up, It may not be running normal numbers due to it is taking it longer to get to normal operating temps. Also, check your oil and all of your filters, that can play a diffeence. How many miles on the truck? Are you still under your 100k/5yr?