I can hardly believe it, but I think I fixed my stalling problem. Upon furthewr inspection, I uncovered a plastic clamp around a wire connector on my ignition module (see attached photo) that was not closed properly. I removed it, cleaned it and reinstalled it. After two days of extensive driving, the D90 has not stalled once
I hope that this fix lasts and that this info will be helpful to someone else with this problem. Thanks again to everyone that offered their advice and assistance.