I'm posting on here what I wrote to you in my PM.
The stalling issue occurred a couple of times early on, but hasn't in quite awhile. Either my car has adapted with timing/fuel adaptations, or I have changed the way I drive my car. I don't ever go from 55+ to neutral.
I'm not sure what caused this, but I suspect the increased free flow of air decreases the vacuum pressure more abruptly during quick changes from higher to lower engine rpms, but temporarily, which exerts control over the idle rpm.