i havent done a scientific study but i feel that PEAK Global antifreeze for import cars seems to work alot better than prestone just an observation. also here are some posts on the topic that might help.
http://www.toyota-supra.info/forums/...ir-w-pics.html
http://www.toyota-supra.info/forums/...et-repair.html
http://www.toyota-supra.info/forums/...-symptoms.html