Overheating engine 2002 Chrysler PT Cruiser overheats after 2 miles, recently replaced water pump, thermostat, timing belt, water pump, and radiator

No milky substance, and if I run the car no faster than 60mph, the temp stays cool, all day, week, months. I'd run it hard at 65-80mph, and it get hot, boiling temperture. I don't think the thermostat is fully opening, and restricting coolan flow. My engine runs fine and like I said no milky stuff in my oil. I am going to pull out my thermostat this weekend and see if the water flows and see if it will overheart. No milky substance, and if I run the car no faster than 60mph, the temp stays cool, all day, week, months. I'd run it hard at 65-80mph, and it get hot, boiling temperture. I don't think the thermostat is fully opening, and restricting coolan flow. My engine runs fine and like I said no milky stuff in my oil. I am going to pull out my thermostat this weekend and see if the water flows and see if it will overheart.