@dipodomysdeserti I don't really get high pressure caps. The cooling system was designed to run at a given pressure and a higher cap just raises the boiling point past the point where engine damage is already going to happen. My 2 cents with toyota Truck cooling systems is keep the condenser clearer, keep the fluid fresh and replace the parts with OE. oh, and make sure all the gaps around the radiator are filled. I've found that Toyota systems work best when the pressure at the face of the radiator is greatest. if there are gaps around the sides, bottom or top of the radiator I close them with that RV seal foam. makes a big difference.
EDIT - with a .9 bar cap, the boiling point is 245-251, well beyond the thermal limits for engine safety. Whats the point of raising it even higher?
If I recall, the limit for the 1fz-fe is 105C before the AC turns off and enrichment begins. (221f) pretty sure the 2uz is around there too, I've seen as high as 217 (103 c) but the AC never kicked out. The UZ seems to like to run about 10 degrees hotter than the fz and from what I hear that's intentional for emissions. so long as you are saying below 105 c I think you have a good healthy cooling system.