Hi John,
Thanks for encouraging me to contribute to the GDP for Canada!
I stopped by our local Canadian Tire here and picked up a 500ml bottle of coolant stop leak. I added it to the rad after draining about 500ml of coolant out.
I ran the engine for about a 1/2 hour. It smoothed out and now runs without any miss (had a slight one once in a while even after getting the plug wires right!). Ran some fuel injector cleaner through it too, and that seemed to really make a difference.
Could it be a LIM gasket and not a head gasket? Perhaps, but for now it seems to have sealed itself.
A class 'A' mechanic I know suggested that cleaning the carbon out of the cylinders (as I have done) also has a tendency to remove any foreign material, including attempts to seal a leaking gasket (head or LIM).
So, I'll hold off pulling it apart for now, but will keep a close eye on it for sure.
Bob