Hey all! I've been dealing with this issue for a while now. My 03 WRX has been overheating, but only after driving for at least an hour (freeway) and then when I exit and drive in traffic lights the temp starts going up. Turning the heater on helps. It all started a year and a half ago during a track day at Laguna Seca. The car didn't have quite enough coolant when I noticed it overheating (fully in red). After I added more coolant it seemed fine but now continues to overheat during slow driving on long drives. I have thought of water pump and thermostat but I believe both would cause the car to overheat faster. Also I guess I should disclose that I have catless turbo back and stage II COBB tuning as far as power mods. Thanks in advance for any help!!