Lots and lots of things need a little explanation where idle settings are concerned
I will be posting up shortly asking those questions
As for stumbling on over run aproaching idle, I found it more of a problem with Alpha N where the VE numbers in the lowest row needed to be knocked right back. The deep vacuum on over run needs far far less fuel. I had EGO turned on and it was removing fuel, but when the engine speed aproached idle, EGO could not respond fast enough to put the fuel back in. Was easy to spot with logs and the fix was just as easy.
Do you have any logs of these over run events that you can look at what the Lambda is doing?
What are your over run fuel cut settings? What about fuel cut under kpa? does your engine draw huge vacuum on over run?
Other things to consider is adding a large advance ramp in the lowest RPM column, say 30 degrees around the row where your idle sits on the table. This will help when the rpm takes a dive below idle set point.
I had stalling issues on over run when i was using 1.0.53 on the 1400 engine. I upgraded to 1.0.73 and those problems almost disapeared, but the main problem is not knowing what the numbers in the settings actualy mean. You end up changing a number and if it makes an improvemnt, you go with it, not really knowing what you have done or why!!