I was just doing a little R&D on a stock GTS here at the shop (taking a break from writing a software manual). I measured the temperature of the collector on a stock GTS with a K type thermocouple. It was a whopping 1150 F degrees at idle. I was looking into the temperature differences of the exhaust pipes between the cylinders also. #'s 1 to 8 were typically 740 degrees F at idle, while # 9 and 10 were between 570 and 640 F.
Sean
Sean