Overheating

I have replaced the water pump and t-stat, water pump was leaking and just changed the t-stat while I was in there. It still keeps overheating. No water or sludge in the oil. Cant find any leaks anywhere and its not loosing fluid. What could it be, maybe just air. I am lost, I have mech. Nearly all my life but this has me puzzled, help.

It is your heater core that controls the thermostat on your car, Pain in ass to replace, but worth it, unfortunately, 6hrs labor ugh!

First, what is the running temperture?
My car runs is at about 220 degrees, if that is to hot, what could be the cause. I put a spectrometer in the over flow to test for gases and got readings of exhaust. Does that mean I need a new head gasket?

I have a2000pontica sunfire replaced the fan relay and fan motor but fan not kicking in and overheating

2000 Pontiac Sunfire, 164,000 miles; My car temperature gage has been maxing out. Since the first time, about two months ago, I have since replaced the thermostat and waterpump. I have pulled the heads out and had them checked at a machine shop. I have replaced the head gasket, valve cover gasket and serpentine belt. I have changed the oil and filter. I have changed the plugs and wires. I have flushed the radiator. What else could possibly be causing the car to overheat after 15 minutes of running it? Please help because I am not trying to buy another car and create another monthly bill!