I'm stumped. I have an intermittent misfire I just cannot solve. Car will run fine for a couple of days then start missing on me. Have checked coils, injectors, replaced plugs and wires. Everything comes up in spec. ECU was rebuilt a couple of years ago.

Problem comes up after a hot start. Runs perfect as long as I don't shut it off. Drove for about an hour today, no problems. Seems to me it must be some component that is getting heat soaked. The only thing I've noticed is the key seems hot when I shut it off. Not sure if that could have any bearing on the problem.

Hope someone can get me pointed in the right direction

I repeat this often just cause ive seen it and know a bit about electronics: The coils can test fine and still be bad. Just like you said, heat can affect them, moisture as well.
Any particular cylinder misfiring? Injector drivers are also a possibility though i hope not.

I've had more than one blue top injector fail only when hot & cause a misfire. Sometimes they set an injector circuit code while problem is occurring, sometimes no code at all.