Hi Steve,
        Your van's symptoms are similiar to my experience with a bad coil.
My van would stall and stumble after warming up. It fooled me a while
because the van would run perfectly at highway speeds. As soon as I
was at low speeds or idle then the problem revealed itself. When I
started to diagnose what was going on in the engine compartment and
as I was poking and pulling on wires, my hand came near the coil and
it was very hot, in fact I couldn't touch it very long. I replaced it
and no more problem. A bad ECU could also be a suspect  as you
mentioned and I also experienced this. However it wasn't an
intermittent event but constant. Hope this helps.

Rick Koller