Misbehaving collant temp kv6

Hey guys, hoping I'm on the right track or if you can steer me otherwise.



My ZT is running like a dream, except yesterday whe giving it some beans in traffic it flicked to red on temp, and threw a coolant overheat warming.



Seconds later this dropped and warning disappeared.



Only does it if it's getting driven with spirit. Set up an obdc connection and took it out for a drive.



On the freeway it's fine. I can see the temp rise and fall which makes me think the thermostat is opening fine. Pull up at some lights the temp rises to 108 then falls but never below 100 until your out on the road again.



When I'm in traffic I'm bound to see it flick up. Watched it last night hover between 115 and 117.



I know all the fan speeds are working, I think that's all that's pulling down the temp.



Heater inside doesn't blow particularly hot air if that is relevant?



Any ideas?



Also at what temp should I be ****ting myself about warping a head.

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