It appears that the real problem to this was simple
Two spark plug wires at the coil pack were full of chaulky like corrosion.
I had pressed on them to make sure that the connection was tight, and it felt OK.
While the shop was putting in a new O2 sensor, I thought I'd make sure they connections were tight and clean... and :o I found this.
So I don't know how much of the problem was O2 sensor, or IAB valve. But it'* likely that it was simply those dastardly wires...
THANKS to all who gave great suggestions, I think I'll continue to use all of them!