Ok, I learn something new every day.
I just got back from having my codes read and there are none. No trouble codes set at all.
The guy at the parts store seemed to think as I originally did; there would be no codes set if the check engine light had never come on but regardless I still have no clue what is causing my problem.
Could the EGR valve be bad without setting any trouble codes?
It doesn't seem like a fuel problem. The problem only occurs when the vehicle is in gear and you come to a stop. I can put the truck in neutral while rolling down the road and it doesn't miss a beat. It is only when the ground speed gets very close to 0. Are there any sensors that coordinate idle speed with ground speed? Just thinking out loud...
Also, where can I get a set of factory service manuals for this truck?