When I burped the Supra I got the engine to normal temp and parked it on a slight hill with the front tires on ramps. I then ran the heater for a while to get the trapped air from the heater core to the highest point in the system, which was now the top of the radiator. After it all cooled down I openned the radiator, the air escaped, and I topped it off with coolant.

On that car the heater core was about the same elevation as the radiator so the air got trapped in a normal system flush and fill. I hope that you have the same problem because another head gasket would suck.