I always thought Ford had a limp mode. Similar thing happened to my bud when we started out on a trip to Death valley. His EGR valve went sour as well. So far, my DuraMax has served me well. However, I do keep it completely stock to include the factory Air cleaner. It is not a daily driver. My fingers are crossed my EGR valve will not cause me an expensive engine rebuild. But who knows? I just try keeping it up to snuff and good to go.
As for Rosewell and the aliens... we saw all sorts of crazy signs, some down-right funny! Entertaining! Interesting city to visit, and the Rosewell GMC/Chevy dealership was amazing service and friendly. My wife got so made that evening she wanted to trade the whole camper and truck in for a new vehicle and drive home. They allowed us to stay in our camper the whole time they worked on it.