Can a maft adjust one bank at a time?
from mixture or just from electrical
variation between two sensors. Especially
as you get further from 0.5V, the response
tends to "saturate" and you can't say that
0.92V means any particular AFR; only that
0.92 is richer than 0.90 -on the same sensor-.
Might try swapping them side for side and see
if the readings move with the sensor. If not,
then it's mixture most likely. If yes, might
want a fresh pair (new should match better,
especially if from same mfg batch).

