Follow up #5
So during the course of 1.5 weeks, I drove very little. Every trip resulted in a CEL with the exact same codes. Reflashed the ROM with no success.
Decided to spray the contacts with electrical cleaner and plugged it back in. Here is the real kicker: I tugged on it to see if it was snug - it was not. I tried to reseat, with no success. I grabbed pliers and pinched the connectors together and heard a click.
Drove around for another hour and a half - P0171 - High airflow/imbalanced AFR. Engine was definitely bogging and this is most likely the ECU retuning to live sensors finally reporting data. Let it cool down and tried again. Solid. Rock solid.
Attempted fix:
Make sure the connector is connected snug with the clip engaged. I believe the mech who installed the headers and therefore the O2 sensors didn't plug it in all the way and cleared the contacts causing intermittent issues. Every time would plug them in would reengage the contacts, but not securely resulting in the repeated codes.
Use angle grips to press the connectors together.
