another thig you might want to check before you rebuild the l.p. system You said the plugs showed alot of wear. while the truck is running unplug each coil pack 1 at a time and see what happens.
sounds kind of like a bad coil pack. each pack unplugged should make a difference in the running till you get to the bad one. if you have a bad one, once its unplugged there will be no difference in the idle.
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