I didn't think the ECT would fix it, but from what you said it was needed anyway. You realize it could be so many things...

I don't think pulling the ECUs did anything except allow you to at least do something and feel less vulnerable to the whims of your car. Any component will fail when the car is moving, as all of the sensors are doing their job whenever the car is running...be it cruising down the highway, or sitting at idle. The fact that you were slowing to a stop, thus indicating something that may be affected by a shift of a wire, or a shift of the fuel, I would look at the relay under the cowl, and I would look at the connections to my air mass meter, my crank sensor, and my cam sensor. I would also fill up my car to see if the problem only occured when I was under the half a tank mark.

Chris