OK, Kurt, you were correct. I should have tested the entire EGR system. Ends up my P0401 code came back "Insufficient EGR Flow". It eventually cleared itself, but now the truck idles at 600 RPM (normal) when cold, then drops to 350-425 when hot. Feels like it will stall. All of this leads me to believe it is the actual EGR valve now. So, next question ... is this an easy swap? Should be right? Just plug and play? Oh, but Kurt, I still need to say , just so I feel a little better. :whoops: Hope you don't mind.