Hi can anyone help ..I have a 2004 subaru impreza  sti  everything fine but fitted some aftermarket gauges and when running all good and reading correct but when I turn any electrical load on the gauges go up like 15deg temp oil and water .  I have ran direct to battery to make sure it's not a wiring problem and still the same I have ran new earths all over the engine and body still the same . Charging at 14.2 and when loads on its 14.0 .

Given what you have completed already - are the sensors getting interference?