Harnish: with the engine running, have you tried wiggling your spark plug wires? Some folks have reported that when they do that, and/or make an ohm/resistance test, they find that the wires have corroded, broken, or frayed, to the point where the electrical conductivity is not 100%. Also, when you pulled the sparkplugs out, did you inspect their condition? What brand/type of spark plugs did you replace the old ones with? Just a few things to look at...--P.D.