Water temp sensor moving with revs

[apg39]

Noticed a small issue just now, (1990 L series, carby) As my revs rise the water temp gauge is rising as well, more prevalent at about 3000rpm+ (don't have a tacho so can't say for sure). Normally runs at 1/3rd on the gauge, as soon as I rev higher it moves to about 2/3rds up. If I let the car idle straight after revving or pop it in neutral while driving it just goes back to normal operating temp. I have replace the water temp sensor on the top left side of the block about 2 months ago so doubt that would be faulty & cars still way to hot to check coolant/oil etc. Car doesn't seem to be driving any worse than normal for a EA82 & no other obvious symptoms of a blown head gasket.

If it was the car overheating I doubt it would go down as soon as the revs drop but I don't really know.

Happened to anyone else before?