Welcome,
Do you know the maintenance history on this truck? When was the last time the fuel filters replaced. I have found with my 03 if I don't change the filters at the 10k mile interval I see a performance hit and it smokes on a hard acceleration. I also notice some sooting on the rocker panel and bumper after towing when the fuel filters are getting old. Also, does this only happen when the engine is cold, or all the time? Just a thought.
Scott