A/F/R gauge for tuning

This is where I believe you could be fooled maybe. Depends on how your o2's or o2 if you only have one are positioned.
In theory if have an o2 placed in the collector of a header you are reading the average of 4 cylinders. 2 could be lean 2 could be rich or any combination. Where you put the sensor could also bias toward 1 or 2 cylinders more than the others. And if it's just on one side you only have data for one side of the motor.
I have o2 sensors on each side of the motor on the dyno and sometimes they vary from side to side. Fuel distribution not usually even for every cylinder. There are many reasons for this. All that said usually when a motor is rich and misfiring my o2's show that the motor rich.
However poor fuel distribution can cause a rich or lean misfire on a single cylinder when the o2 average looks normal. I can usually pick this out by looking at individual cylinder exhaust temperatures.