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I've yet to get an answer, but if you have the tune that deletes the rear o2 sensors, I wonder if it's even necessary to have them installed at all. Why not just unplug them and remove them and place the cats right in their place.
I know that the RR Tune disables the CEL associated with catalytic function, but all other O2 related CELs remain active. For example, I had a pretty bad exhaust leak at the header/exhaust connection and it triggered a CEL while on RR tune.
Rear o2 only monitors the cat efficiency. No cats, and the rear o2's disabled, I don't believe they even need to be in place. That is unless the tune still requires seeing some sort of signal across them and is merely altering its reading.
Was your exhaust leak at the header connection and/or was it a front o2 fault?