Results -- mechanic found no codes, no problems, kept the truck for three days and started it numerous time, including first thing in AM.
He and shop foreman spent lots of time with this, and lots of time with me trying to figure it out, and explaning what they did. But could find nothing wrong with it ...
MY guesses:
Guess One: Some minor glitch in a module or the computer was a bit out of sync and when he re-set everything, it just synchronized as it should. So, he found nothing wrong. All settings in the proper position - so, now it shows no codes or tech troubles.
Possibly a bit of dust or grit blew out, or dropped off one of the contacts (or moisture?). Maybe left over from the original assembly.
Guess Two: A tank of bad gas that took a bit of miles to clear out ...
Guess Three: Moisture in the module or computer - either from the original assembly or due to the rain and humid climate. We are now in dry climate (Texas = dealer) and so, will not know if moisture continues to be an issue until we return to the humid areas in the south. Could be a temporary thing, gone now, or could be a seal issue where moisture gets into the electronics whenever its humid or wet. That would be a true bummer ... but possible.
My first thought is Number One ... second, but not as unlikely, number two, the third guess would be a true nightmare.
I didn't own the truck long enough to have any comparative driving experience with it. But once we got back on the road, the mileage jumped to 10.5 on the flat (hauling TC) (up from 9.5) and that was one mpg more for at least the first tank. Then we hit the hills and all mpg bets are off there anyway.
It now purrs like a kitten, hauls like a truck should, and runs smooth on the highways. Starts every time on the first crank spin ... So, time and climate variation will tell us eventually. But for now, we're really enjoying the new truck, its performance, and the trip west. In Tucson now and heading for Death Valley this weekend.
One more thing I mentioned in another post - throttle lag, and others have mentioned it too in new trucks of all makes. Happens in a lot of new trucks - drove five or six with it (a slight delay when you push the accelerator) ... this truck did not exhibit that delay and still does not.
From a dead stop or accelerating to pass, it gets instant response. Apparently, that's unusual - so, happy about that anyway -- and is one reason I chose this truck instead of others we drove.