Gonna get right to it. 2005 Mustang GT, 3V 4.6. Replaced all components of the cooling system and everything is flowing how it should. Pressure tested the system and there are no leaks. All air has been bled from the system and will maintain 210degrees all day long at an idle. As soon as you give the car any pedal, either under load or no load, air gets back in the system and temp rises to about 216degrees and will not come back down until you open the bleeder screw. If you don’t bleed it, it will continue to rise. Did a compression test and number 5&6, which are adjacent cylinders, were about 10-15 PSI than every other cylinder. I’m thinking it’s the head gasket, does anyone have another opinion?