Ok... Lets tune you in... Stock shut down temp is 170*F worth of coolant. As for starting of the different modes automatically...

High idle starts at below +32*F of IAT temp. (With grid heaters which is about 25*F outside)
3 Cylinder high idle starts at below +15*F of IAT temp (With grid heaters which is about 5*F outside).

Like I said you could build the IAT fooler switch and then gain selection of the 3 cylinder mode... :humm: