I had a similar problem with two of my fords in the past five years. Have you had anyone check the power control unit for the engine itself? Sometimes the brains of the computer for the engine gets some glitch and had to be cleared and reset before the problem went away. The PCU or ECU or whatever they called it was sending wrong information to the engine, killing the power. Car would almost die on me, but engine kept running but would not get any response from the throttles. The vehicle in question was a 2007 and a 2009 Ford Focus with the L4 engine. Maybe something similar to that is happening here. Each time the car did this, the little wrench looking light would come on. Each time I took it to the dealer for checking out, the light would not come on and they said they could not do anything about it. It was very frustrating. Only after forcing them to reset the PCU did the problem finally go away for good.