I'm using OS 12212156 (non-COS) and trying to turn off all fuel trims at idle. Clearly something is going on because (with a cold start) the engine idles well for several minutes then suddenly starts wild AFR fluctuations. This even though STFT & LTFT both indicate 0 adjustment. I cannot find B3647 in my tune file so I assume it is not in OS 12212156. But I think I understand the idea. So if I set B3601 to (for instance 14.5:1), do I avoid semi-open loop at idle? Or, do I also need to set the AFR #s in B3605 to something less than 14.68? If I do, will STFT / LTFT operate correctly when the throttle angle is above the max idle throttle angle?