I have a 94 camry v-6 that only overheats at highway speeds. Does not heat up in town. I have changed w/p, rad./ t-stat. and cap. Does not use any water and no steam from exhaust. The fan works as it should with engine rpm's. HELP!

"The fan works as it should with engine rpm's."

I don't understand this statement.

It is possible your bottom (suction) hose is collapsing under load. Also, your thermostat may not be opening up all the way. Did you buy a Toyota thermostat? If not, that may be the reason. Did you install the thermostat correctly? (just checking)

do you drive with the AC on