I have had this problem for sometime now with the truck idling rough in Park. All injectors have been replaced, and the Rail Sensor. Runs much better but every once in awhile it will come back. In speaking with my mechanic, he thinks that it could be one or more of the wiring harness to the injectors giving intermittent signals to the injectors. I have posted this problem on here before and I find it funny that I appear to be the only one who has had this problem! 
