I had similar problems when I first got my car. It ran at good temps while driving but as soon as I sat in traffic for any length of time the temp shot up to 200 plus. It took a while but after boiling out the radiator, changing the thermostat to a 160, putting a coil spring in the lower hose so it wouldn't collapse, flushing out the block, changing the water pump pulley to a smaller diameter to speed up the pump, and changing the pump to a Flowcooler water pump, it has pretty well solved the problem. Driving the car to Carlisle in that unusual heat last year, a 300 mile trip for me, it stayed right around 185-190 while driving. For the short periods of stopped driving it would go to around 200 and still ran good. The only time I had problems was on the way home when we got stuck in a 3 mile backup. Then the temp shot up to 210-220 and was a bitch to keep running. I had to take it out of gear and rev the engine up some to keep the water moving, and to keep it running. Otherwise it would have stalled.