Like mentioned before, are you SURE your thermostat is in properly? Using stock radiator and stock fans, you should NEVER overheat at idle..if you are using a GST radiator, and high volume fans, and still overheating, something is def not right at all..Does your driver side fan come on at all when idling? The ECU turns the driver side fan on at around 206 degrees. It turns off at around 195 degrees or so. If you fan is not turning on at all, then that is your problem. Since you are not moving, there is no airflow over the radiator, which means the fan NEEDS to turn on at some point, which is should be doing at 206 degrees. If its not, then that is your problem. If your fan is turning on, and still overheating, then something is just not right. Do you get hot air from your heater? Pressure test your cooling system also..Could be a bad radiator cap too..Bad caps can cause very low pressure in the cooling system which can cause overheating. If everything checks out fine, then I'd say its most def your headgasket. A compression test will not usually verify this though, you need to do a leakdown test. YOu can buy leakdown testers at parts stores, and you need compressed air to use them..