I have a totally different theory. I think the rich condition in CL is caused by sudden "Tip-in" enrichment, which affects STFT, becoming LTFT. This is then passed on to OL. I think Tip-in should have a lower threshold, and smoother transitions, so it wouldn't adversely affect fuel trims in CL, and then corrupting OL. It doesn't require any mysterious ECU reverse engineering, and it is a fuel source outside of usual channels unaffected by the MAF or MAP sensors. What do you think @
thambu19?