The thing to do with the gauges is to get used to what they normally show and only worry if they start showing something different - ignore the numbers. As long as the sensor to the ECU is working right, the gauge is just to warn you of a change in the status quo.
My coolant temp gauge always shows 5-10 degC less than the Emerald software gets from the main sensor, my voltage gauge is always 1V less than a multimeter across the battery and the less said about my fuel gauge, the better
If you want accurate gauges, buy a normal car...