If you want my honest opinion, stop running the heet, the problem should go away. In my opinion, its possible the methanol is going to take the narrow band o2 outside of the perimeters the computer uses, and stall the engine by continuing to retard timing.

This car has a warm up circuit, etc. If you have winter gas in winter, etc, you should have no use for additional additives. Gas companies put "more" in gas today than they have in previous years. I have only run "additives" in old gas, and even those times i bought straight methanol, etc. NOT those bottles where you don't know what else is in them. Not that I am telling you to go buy a gallon of denatured alcohol at home depot and pour it in your tank. But I am wandering.. Back on subject.

Is it about the same time of year as it happening the last time? recently after switching to running heet?