I had the same problem wit my 06 f350. I also had no engine light and mine would change idol speeds for no reason and sometimes almost stall out. it would go from 750rpm to 450rpm to 1100rpm and back to 750. I replace the pedal because I thought is was a TPS issue. turns out there was actually a broken piece on some bit if the electronic module for the turbo. the shop didn't figure it out until I decided to have them take the turbo apart to check and see if the ring inside was corroded and sticking against the vanes in the turbo. they found the problem after they took the turbo out. I also had the ring inside the turbo replaced with an upgraded one since it was apart anyway and I also had the oil drain tube replaced with a larger diameter one that ford was pushing people to replace because it allows oil to move through the turbo quicker reducing sludge build up in side it, (I think it was also a recall). also had a new spring put in the small fuel filter on top of the engine to increase fuel pressure. all in all, $575 for everything including labor. if it turns out that the electronic module is the problem you are having, I would suggest doing all of this as well, truck now has very little turbo lag, (almost none) more boost, maintains higher boost at cruising speed and gets better MPG. I would suggest cleaning the EGR valve as well, it wasn't my issue but it was in need of cleaning, a vac., some carb cleaner and a rag is all you will need for that (do it yourself, that one is easy, takes 30 min. tops). you should also get into it one or two times a week, the turbo in the 6.0 doesn't like to be babied. it is a variable vane turbo and needs to be worked a bit to maintain full range of motion. hope this helps ya.
Last edited by hollywood7721; 06-10-2013 at 05:06 PM.