My car had a hesitation issue when it was cold too. Also had part of the problem you are explaining as heatsoak. It happened twice. First thing was the valve cover gasket had sprung a leak and had filled up the area aroung plug #1 with hot oil. That was causing the spark to get free. The other one was bad plug wires. After both of those left, the problem pretty much went away!
I do know I have a small heatsoak issue though. Going on what you were explaining with the heat, I have it too, but I have a hollowed airbox!
