Hi John: I have the same truck and had real bad mpg also, I have done a ton of add-on's to try and improve my mileage (I am master tech with ASE) I couldn't find the problem. I just got done with a class at our local collage where the instructor had been the diesel tech at a local Ford dealership. He gave me enough information to test my own truck. I found that the 5 volt referance to the map sensor was not steady, it had a bad splice at connection at splice # 120 in the engine wireing harness. What that did was make the PCM drop into a preprogramed driving condition which would not control the timming or the fuel control. I ran a second wire from the PCM to the map sensor and cleared all the codes. I didn't check the mileage yet, but with a round trip to the collage and back I could see a great differance in the amount of drop in the fuel gague. My guess is I doubled the mileage. I was getting about 10 1/2 to 11 mpg loaded or not - up hill or down, didn't make any differance at all. I will ck with ASC and see if they have a shop well trained in diesels in your area and let you know. Good luck Mike OB
