Roger, Appreciate your sitting in on this one... Flew today prior to reading your post. It was warm enough, 65F, that I didn't pre-heat. Made a special effort to remove choke input as soon as possible. Preflight runup was OK, better than before. Again, even better post-flight. I wonder if my cold weather preheat with air forced up from below was somehow affecting the modules pre-start. I will try the icepack as that sounds like an interesting experiment. What is the procedure for swapping the plug wires at the modules? Or the page number in the shop manual.
My plane has always liked to start with little or no choke input. Could my carbs be out of adjustment in some way? I have never messed with the factory settings except to balance them annually. TIA, Jim