The A/F will tell the complete story. Ford contol units will always add more fuel when a o2 goes on the blink to make sure there is not a lean condition, my Crown Vic. did it.

I do not know about retarding the timing too. Make sure none of the wires going into the o2 sensor are rubbing on anything or are freyed which would cause the sensor to ground out.

BTW how was the turnout for your MMTB track day ?