No EFI on mine, all I can see is the gauge movement. When the car is warming up the factory gauge comes up slowly, the aftermarket one stays on zero. When the thermostat opens, the aftermarket one blasts up to 180 in a couple seconds. Depending on the temp outside, the aftermarket gauge seems to cycle from about 175 to 190. I don’t know how accurate it is, but seems reasonably close as I have a 180 t stat.
