do you have an electric fan on your rad? at high speeds it may block the wind flo. how fast are you driving? check all fluids, maybe your water pump too. the water pump is a rubber wheel and may be rotted, at high rpms it might not be effective. Just a few things to look at
have you never seen a toyota water pump?? true the water pump fins "could" be rotted, but you need to know NOTHING in the 22R water pump is made of rubber, except the tiny seals
slow down? drink faster? maybe that might work
Its not a head gasket problem, and DONT FLUSH YOUR MOTOR EVER!!! not with bilstien or any 
like that, you will lose compression and shorten the life or your motor. and an engine flush would have nothing to do with this problem.
what planet are you from??
where is the temp getting read from? check and make sure the wire is not touching the exhuast manifold or that the coil that goes around it itsnt touching anything either
the temp wires are on the passenger side of a toyota truck,
what coil?? if you mean an aftermarket temp guage with the coiled wire protector, why would it be anywhere near the exhaust??
