Just got back from meeting w/service. Car had the stumble on the way there but would not re-exhibit the behavior with the service manager and tech in the car. Apparently all adaptations have been redone multiple times.

In speaking with the svc manager the possibility came up that maybe the torque converter was not unlocking when coming to a stop, thus dragging the engine town to a too-low idle? I had another car where I could lock the converter with a switch, and I remember if I left it locked when coming to a stop the same thing would happen as what's going on now. Is this plausible or anyone else see a similar issue?