When hot outside car does not want to idle
 

My 850 GLT runs great, just had new head gasket done, new time belt, water pump, all of the PCV system etc. New spark plugs and wires and a new altenator. I drove it from Ogden Utah to Tacoma Washington and back without any issues until I stopped at a rest area near Boise. I left the engine on while I ran to the bathroom so my wife could stay cool with the AC on. I got back and the car had shut off on its own, tried to start it and after a long crank it ran, but very rough. I got it on the freeway and it felt great. It was about 100 degrees out at the time. Now every time its hot outside it wont last long at a red light or other longer stop. It works great in the evening etc, I'm at a loss please help.

mine was acting up when hot. put a different ignition coil in and haven't had a problem since