Encountering a similar problem with my 1995 USDM GSR / B18C1 OBD1.
4 minutes after driving, regardless of cold start or long warmup, CEL triggers code 43. Driveability normal.
If I cycle the key or turn the whole car off and on, code clears, STAYS cleared, Driveability suffers. Partial throttle input has intermittent (but persistent) cutout until MORE throttle is given, then it jolts to life. It’s a very rough ride.
Driveability usually eventually clears, but for not particular reason.
Spark plug 1 looks normal if not a little lean. 2-4 are sooty as if they are running too rich.
My AFR gauge always reads deep into the Lean, unknown 02 Sensor, but it is on the end of an extension harness that shoots good.
Cylinder 3 has a leaky valve stem seal that will be replaced this weekend. I will be changing the fuel pump and filter at the same time (it’s time for the filter and I wanted to put in a 255lph pump).
My suspicions are the pump or 02 sensor. What else could I be missing?