Supra has 4 cylinders full of water

[Jebus]

I really feel for you guys. All i can say is that the majority of problems with this engine come from coolant and maintainence. I'm in the final stages of a full rebuild, about to put engine back in car. My engine had signs of all the problems you guys have mentioned but not as bad, i was lucky. $130 bucks to preasure test and surface the head, $600 bucks on parts, all a bit under trade as they were organized by a mechanic who helped with the rebuild. All cleaning i did myself, and the bore was honed by my mechanic, i saved heaps, and have been told it will last like any engine as long as i dont put straight water in it,(it eats the engine and cause a heap of problems) and service it like any car. THats it. All coolant pipes and lines have been replaced and im going to use the Toyota Red coolant, it really is good stuff and you dont have to change it like your oil so its worth any extra it cost.
And, if you do decide to do a full build check things like oil pressure before you start it, make sure oil cooler and heater box have been cleaned, and everything torqued right. Goodluck.