Question about the girlfriend and her truck. Does the truck get plenty of highway miles? Or is it a lightly used, around town truck? These engines, and especially the turbo, thrive on being used a lot and used hard. If this is the first CEL, it might be worth running the crap outta the truck for a good long highway run. Climb some mountain grades. Get her hot (the truck, girlfriend optional). See what happens, and in particular watch that boost gauge. It should never be above 28-29#. After that, see what happens before you tear into it.