Just a point of info, the stock FI head has two temperature sensitive devices in the cylinder head. The first, above spark plug #2 is of course the sending unit for the instrument panel temperature gauge, and this item is common to all X1/9s, be they FI or carbed. Very close to it, near plug #3, is an FI-specific item called the Thermo-Time switch (FIAT part # 4393600). This also senses temperature and depending upon the temp, it will activate the Cold Start Injector located on the end of the intake plenum log. Based also on temp, it sends current to the internal heater of the Auxiliary Air Valve, to help it heat up at the correct rate.
Finally, as you know, the Bosch FI coolant temperature sensor which sends its info to the FI controller, is located in the FI-specific thermostat housing.