Have you replaced the coolant temp sensor? Not sure on exact name but its the sensor on the thermostat housing. The SPI is a different animal but had a odd problem with it. At cold it wouldn't start tried everything. Eventually it would but wasnt happy till warmed up. Finally one day the gauge literally went from one side to the other a few times or never would of found it. Good luck..
02 Focus LX 114k - auto
04 Escape XLT 132k