Thanks for all the info so far.
Mike - gas cap is a different code, but on Saturday I did "reinstall" the gas cap anyway just in case.

Hey, I like the idea of switching parts with the Fronty - why didn't I think of that - lol. I'd probably have to go do a different dealer though.
"Yes, the X mysteriously fixed itself, but could you check out the Fronty?"

I recall seeing that if I change the MAFS, I need to tell the truck's computer about it somehow. Didn't dig deep enough to see if it's just a key turning kind of procedure (like resetting the airbag light), or if you have to hook up something special the tell the computer about the new MAFS.

For now it's a waiting game. At least it's not a critical part when it fails - I can still drive the truck.

Honestly I can't tell the difference.
Guess I'll check gas mileage though. This stupid MAFS must do something productive?
Actually, the error code indicates LEAN mixture, so maybe my milage is higher with out itf!