Running rich is based off the visual observation of a black tail pipe.
Not real reliable.
The computer is commanding the fuel to lean out I assume because it is sensing it is running rich.
The computer is in lean-command, trying to get the
actual air-fuel mixture to the desired 14.7:1. IF the O2 sensor is showing the expected swing between low- and high-voltage, the mixture is "correct", averaging neither rich nor lean.
The o2 sensor is cycling between .4 and 800 MV constantly. Which appears to be normal.
.4 mV and 800 mV? Or 400mV and 800mV?
400 to 800 mV would indeed be "rich". I don't think I've ever seen an O2 sensor go down as far as .4 mV, but a swing from very low to very high voltage is normal for a properly-functioning O2 sensor.
I was looking at the spay patterns on the injectors and the right bank looks like a denser spray than the left. Both injectors are remanufactured and were replaced today.
Let us know how that goes.
For the record, the "right-side injector" does not feed only the "right bank". Both injectors feed two cylinders on each bank--the two outer cylinders on one bank, the two inner cylinders on the other bank.
One injector feeds 1, 7 (outer left bank) and 4, 6 (inner right bank).
The other injector feeds 2, 8 (outer right bank) and 3, 5 (inner left bank).
Therefore, a TBI with only one O2 sensor, is still sensing the fuel output of both injectors.
I think I found a possible culprit. The EGR solenoid is pulling vacuum at idle.
New EGR cleaned up the idle but it's still commanding a lean condition.
Good catch on the EGR.
It's not commanding a lean condition. It's in lean-command, trying to get to a CORRECT air-fuel ratio. Lean-command is reducing the "expected" amount of fuel according to the base programming because for some reason the base programming would be too rich on your engine. For example, excessive fuel pressure. The O2 sensor (if it's working properly) is the best way to determine rich/lean, and yours seems to be showing a proper air-fuel ratio once the fuel trims are in lean-command.
What is your fuel pressure?