dumb overheating AGAIN

[LagunengrunE36]

Is your aux fan working?

[lolcantturn]

The wierd part is reving it at standstill makes a difference.

I'm talking about I have to go to 5k to make a difference. In first gear I just get off normally and it drops.

Are you sure your gauge isn't acting up?

I don't think so..if it is, then it's a very evil device.

[Eecen]

Are you sure your gauge isn't acting up?

[Dude]

The wierd part is reving it at standstill makes a difference.

[lolcantturn]

Well it's not overheating, but it slowly crawls to the 3/4ths mark on the temp gauge. And I don't understand why.
If I rev it pretty high or if I'm leaving at first gear, it'll drop to halfway, so something is happening when the car is under load.
If I'm idling, within 6 minutes it'll go to the 3/4ths mark. But of course I don't let that happen, but I know it will.
Here's whats been changed
New Radiator
New Water pump
new hoses
New thermostat
New headgasket
New Coolant Temperature sensor
It's been bled pretty well I'd say

Occasionally, it'll act completely normal and never go past the half mark at all, and sometimes even be a little bit before the half mark.
Doesn't make much sense to me. Help?