The closest I've seen for a fix is over on the ih8mud.com Land Cruiser board. They determined what resistors need to be swapped to get the gauge to read more precisely.

The logic behind the OEM gauge is that if it reads TOO accurately, meaning you see the needle move with only a few degrees of temp change, would send owners running to Toyota complaining the gauge was either broken or the truck is overheating. So, they put in a resistor that keeps the needle steady at the half way point and it doesn't move up or down for a broader temperature swing.

I do not know if the same resistor swaps as used on the ih8mud.com board are possible for a truck/4runner, but it's a start.