http://www.supraforums.com/forum/archive/index.php/t-474193.html
From titan
This thermostat opens your radiator at 160 degrees instead of the 180 degrees your stock thermostat opens your radiator.
Although we recommend this upgrade to everyone, it is especially important if you live in a hot area, have a built motor, auto-cross, or road-race.
If you’re looking for a thermostat to help your Toyota’s cooling system reach its full potential, then look no further. The TRD Japan high performance thermostat will deliver! Most stock Toyota thermostats open between 180-190 degrees Fahrenheit to cool your engine, which is fine for normal driving conditions. But if you use your Toyota for performance driving or just want peace of mind protection from intense heat, the TRD Japan high performance thermostat opens at 160 degrees F to quickly cool your hard working engine.