Also the next chance you get the truck in total darkness open the hood with the top engine cover off. Be careful not to chop your fingers off on the fan since your in the dark (lol) and look at the coil packs. Once your eyes adjust you will be able to see a little bit of flickering through the boots. It should be *very* faint.. just a flicker. All of these should look the same. If you see one that is not really doing much at idle compared to the others then that is your problem.

You could still have a screwed up plug under the pack though. Also, if you see one or more packs that the arc is visible outside that is a failure as well. I had a couple that were arcing out of the pack on to the valve covers. At times you could even hear it pop.