Change out the cap and rotor. Severe corrosion on the posts in the cap. Reddish stain in cap around perimeter - looks like it could have been moisture being slung off rotor onto inside cap wall. Found one screen, popped it out. Was very, very clean. Huynted for the second one, spun engine a couple of times to move rotor base for better view. (This was the point in my adventure where the blood started to flow. Minor cut on wrist.) Put rotor and cap on tighten down screws on cap, gave cap a shake to make sure it was tight. It wasn't.
Started procedure again, still loose. Took cap back out, tried another pair of screws that came in the box. Tightened up good. Wondering if maybe I missed this when I changed cap and rotor a year ago.
Started up truck. Not a hint of misses. Sounds like it did when new. Shut it off, attached scanner, and yes. new code. Assuming that this was developed when I cranked the engine to look for thew second screen. I had two plugs disconnected up top for better working room. Cleared the code and things seem good.
I want to thank all of you for your willingness to share your knowledge. Seems to me that's what good neighbors always did for each other. I hope I can pay you, or someone else back in-kind.
Thanks again for your help.