update from what Sean mentioned...

i replaced injector #8, same issue O2 goes to max lean
unplug injector #8, O2 issue goes away

Sean asked to unplug injector #7, so all others plugged in - pulled #7, O2 issue goes away, plug back in O2 issue comes back
to further test, I pulled injector #1 (on bank 1), with all others plugged in, O2 issue (on bank#2) goes away

so it seems that having all 8 injectors plugged in (electrically) the O2 issue occurs on bank #2

it's always bank #2 O2 issues, never bank #1
the O2 issue only occurs when all 8 injectors are plugged in
the O2 issue goes away when just one of the injectors is unplugged