[Tiamat-red]

Correct, when it goes lean it no longer bounces. It just stays put about halfway between "off the scale low", and stoich.
I know the A/F gauge is not wideband, and not really a diagnostic tool, but as I said it's good for making guesses...i.e. normal or not normal...

After I changed the FPR it drove different. Stronger, smoother, and the right side was "normal" on the gauge. Of course I don't know what it was before because I had the gauge on the left side.
But anyway, I also changed the starter a day before. At which point I had the battery unplugged. Clearing the ECU...
So the difference in driving may be that.

I'm just going to drive around for a couple of days with the O2 sensors switched and see if I get any codes on that side.
Maybe it was the FPR.
Maybe you are right and it is the sensor. I hope so. An easy fix, and relatively(for this car) cheap at $65.
I also have a long trip coming up so I can see if it's(whatever IT is) affected by heat soak.

Thanks, though for the help!