Thanks guys. Quick question: Wouldn't the OBDII system report faulty O2 sensor(s) and or faulty AFM?
FWIW, there were two missing bolts of the four between the air cleaner housing and the hose that connects to the throttle body inlet, creating a fairly good sized leak on the clean side of the air flow. We replaced those bolts and fixed that leak.
I assumed that when the code said "open #4 injector" that it meant electrically open, therefore not energizing and opening to let fuel through.