I'm definitely leaning towards a ground. There doesn't appear to be a rhym or reason to when it does or doesn't misfire. And it's always cylinder 4 so I'd seriously doubt anything timing related.
I've got it down to a misfire on cylinder 4 only.... New plugs, new coils, new fuel system, compression tests at 150lbs. I'm stumped. Guys at kinetic said next step would be to check timing and then valves...