My only other comment is check that bank 1 O2 is in correct pipe and not actually monitoring bank 2. Doing so would cause fueling issues with improper feedback to ecm
If memory serves...US spec 93 has one O2 sensor for Cyl 1-3 and a second O2 for Cyl 4-6.
Assuming JDM = US Spec with respect to emissions controls and O2 sensors, sounds like feedback to ECM is cyls 1-3 only.
Having said that, your description of sensors sounds like front sensors (plural)...