Hey folks,

I'm having some issues with my '90 not staying in closed loop. I've recently replaced the o2 sensor (Bosch), injectors (12 hole from KSuspension), and did the big 7 electrical upgrade, among many odds and ends. I also have the Renix Engine Monitor.

It'll go into closed loop, but ST quickly (about 10 seconds) drops to 0 and then it reenters open loop. It tries this a few times before just staying in open loop.

Idle is a bit rough after initially starting up the car. o2 reading is rich (.3-.5). Gas mileage seems pretty poor.

Things I've considered:
-Top operating temp only getting up to ~180. I've read that this can impact the ecu going into closed loop, but it seems strange for the car to be running rich all the time anyways?
-I've seen other folks successfully use the ksuspension 12 hole injectors. But, could those be an issue?
-Could I have a faulty new o2 sensor? I've seen some mention that the NGK/NTK o2 sensors are preferable.
-Is another sensor faulty that I'm missing?
-Could a vacuum leak be causing the issue? I have replaced all the vacuum lines but who knows?