Joined this site to try to garner some help on various probs. w/05 F250, auto, 6L diesel. My truck is very sluggish between shifts first driving after cold temp. starts, Also, since mid winter past, I have been hearing a "deep growl" between shifts on deceleration-and recently, I hear it between shifts on a medium acceleration. It seems to happen when the tach momentarily drops just prior to the next upshift. My local dealership service department tells me it's normal. (It didn't do it prior til this winter, so it's not "normal"!) I saw a tech bulletin on this site that refers the mechanic to check certain things on the turbo but I'm pretty sure they haven't done this. Has anyone experienced such symptoms and what was the outcome?