[BALLSS]

An exhaust leak on the driver side is your #1 suspect, which the O2 sensor reads as lean, and the PCM commands more fuel to that bank.
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look at your rear exhaust bolt to see if it is missing, loose or the manifold is cracked in that area. rear exhaust bolt on iron heads have a history of breaking

 

[BALLSS]

The rear exhaust bolt is broken off, has been since I got the car 7 years ago, .

...well your 02 see's it leaking as it is seeing more air so PCM commands fuel which is why that bank is running rich.

you need to fix the broken bolt