If I am driving with a small trailer on the back of my 2004 F-350 and I am driving up hills it seems to cough until you really put your foot into it, then it runs fine until you get to the next hill, it even does it going up small hills it seems to sputter.

Go over basic diesel maintenace items--purging water and changing air and fuel filters. See other suggestions in the link below, and in the diesel section of the Sticky:

https://www.askmehelpdesk.com/cars-t...ml#post1415281

My guess is water in fuel filter, if you have never changed the filter, do it now. Not sure about your model but the fuel filter may have a drain valve. Put a clear clean container underneath, drain a couple of ounces, check for water ?

My first thought was fuel filter too. ))