[T77911S]

how old is the O2 sensor
you could still have computer problem.
when you disconnect the O2 it goes open loop mode, also goes open loop about 3500.
when it does this the frequency valve goes to a set freq and AFR is basically set based on the CP setting and the mixture setting.
in closed loop AFR is still based on those settings BUT the AFR is adjusted by changing the duty cycle of the freq valve.
there is also a throttle switch that tells the computer when It is idling and WOT.

you really need to see what the AFR's are doing at idle, 3k rpm and WOT.
I would also check the FV. check to see if it is working and the duty cycle.

if nothing else, get it running good without the O2. set the mixture to spec, connect the O2.
if you still have an issue then look at the electronics.