High co emission at high idle

Hello There

My Chevrolet epica is faild on NCT ON high idle Only

2 Months ago its faild on Lambda and very high CO it was 1.98 VOL 0.20 The limit I changed the lambda, air oil filters new oil than took it into a garage check emission the guy said its jmping between 0.10 and 0.40 it could be a dirty throttle body or bud temperature sensor.I checkd the throttle body it was dead clean and replaced the temperature sensor than took it to NCT again/It FAILD on HIGH CO on High idle 0.32. The guy said he cant get it past because it wont stay long enough under the limit its jumping. So my question is what possible cause this problem(i have to mention it HC CO2 O2 everything very low) and one more thing my air fuel ratio is 9.76:1 I think its runing rich shouldby 14.7 isnt it?
And I think my thermostat not working properly because its stay down very long and when its heats up drups down a bit than up again is this cuold be related to running rich? And I have a bit rough idle when the engine cold or warm. Otherwise driving well

so any help would be great

Thank you