I have replaced the wp,thermastat,had the system flushed, new radiator,new hoses, had the timing set, new oxygen sensor, new temp sending unit, I have the fan running all the time, the air dam is in place and it still runs up to 240-260 when you get on the road and start driving.I also checked the heads and found no problems and no leaks no where. I also replaced the rad cap.

 

Since you appear to have fixed all the obvious caused for the engine to overheat, there are only a couple of other things that can cause the problem.

1. Engine is running lean. Clogged fuel filter, weak fuel pump, too many mods for injectors are your choices here.

2. Ignition timing. If the timing is way out of whack, the motor will overheat as well.

3. Blown head gasket. Not as likely but will cause the problem. A leak into the combustion chamber can cause the engine to pump air into the water passages and the engine can't cool properly. On a cold engine remove cap and look for air bubbles when you start the car. A few are generally normal but if it keeps bubbling that's bad.