I have a 97 with the 5.4 and she has about 187000 miles. in some cases when i accelerate hard, like going up a steep hill or trying to make a red light, the truck gets up to the 4000 rpm range. sometimes when i do this and come to a stop, the truck vibrates/shakes, almost like the timing is off or something. then when i drive for a while and come to a stop again, the vibration is gone. anyone have a clue what this could be? any help is appreciated. thanks!