I have a 2005 F250 4x4 with 60000 miles sometimes when sitting waiting at a stop light and get ready to take off the engine wont respond until I give it more pedal it acts as if it is going to die it also does this when going down the road and it feels like the engine is dead but when you give it more pedal it will take off and usually blow out black smoke I just had the oil changed,transmission serviced ,and both fuel filters replaced and it still does this,any help would be greatly appreciated,thanx