My truck also ran rough until I pulled the plug wires off one at a time to determine if it made any difference in the way it ran.
Got to the 5th plug and when I pulled it off the engine didn't run any worse, so I pulled the plug, put in a new one and fired it up. Ran like a top.
The plugs were Delco R45's and had probably 50 miles on them. Bad plugs can happen even if they are new. I never would have thought it.
