A very specfic transient issue. I'd suggest changing your routine to see if it's time, distance or road conditions. This may help pinpoint the issue. I'd suggest finding a buddy with a scan tool to record the event. Look carefully at the fuel trim, ECT, timing, and any other voltages that change before and during this event.
My WA guess is that it sees a change in the coolant temp, changes the fuel curve and/or the idle air, and it dies.
