Does anyone know if these engines are slow to throw a code when there is a problem? I'm only asking because I'm thinking that maybe there is small problem with the way the engine is running. Its got a slightly rough idle, not sure if its a small misfire or something maybe with a vacuum or egr... anything like that... and when you crank the rpms to 1000, 2000, its just magnified... does that sound reasonable?
Also ran the truck up to 3000 rpm today and it has that rumble vibe again, but at a slightly higher pitch... seems its coming in 1000 rpm steps.