6A11 temperature gauge fluctuation problem

[senator]

I have a 1993 galant engine model 6A11 1800 V6 with a temperature gauge problem.

At idle the temperatue gauge goes hot then cold up and down.
if I bring the revs up it starts to come down then will rise again. when return to idle comes down then rises up slightly from normal.
It does push water into the overflow tank. headgaskests and thermostat and waterpump have been replaced.

this is puzzling me greatly as i have exhausted just about every possible senario.

any help in solving this annoying problem would be greatly appreciated

cheers