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Orian.. Keep in mind you are posting in RX300 forum and the picture you shared is of a different engine than that of a RX. You will get more accurate advice if you post in IS forum.
IMHO ... if you dont have a problem... like preignition or engine run-on after turning the ignition key off .. then stay away from doing un-natural things. Lot of bad things can happen when a well intentioned 'improvement' is tried. I grew up with a diesel car, and those are high compression engines ... where introduction of water in the chamber leads to a disaster.
Agree totally with salimshah, you have to be very careful with water injection, you run the risk of hydrolock if not done properly which could cost you a lot of damage.
This works well, but the water has to be controlled. Race the engine at around 2500 rpm and then use a bottle with a hose to hook to intake vacuum. I would have a helper as you are going to want to control the amount of water with a clothes pin or something to control the amount of water. Let the engine have enough water to just make it partially stutter and then back off. You DO NOT WANT to hydrolock the engine. Personally I would only do this to clean the catalytic converter. I would use sea foam in the gas to clean the valves. Do the water at your own risk....