I'm looking into going single turbo on my 94 RX7 (GT35r, aiming for about 16 PSI) and am at an impasse as to which water injection kit will work best with my setup. Any suggestions?

 

There are 4 major water/alcohol injection kit makers: AEM, Devil's Own, Aquamist & Coolingmist.

Aquamist has the high-end ($$$) kits with progressive controllers and built-in fail-safes, while the other 3 offer very similar kits (price-wise and what's included). The basic kits will use check valves to prevent the engine from siphoning water under vacuum, but a solenoid is a better option. There is a lot of information on the Aquamist and Devil's Own forums, as well as the aux. injection section of this forum. There are a lot of ways to go; it will mostly just depend on price, tank size/location, nozzle size & fail-safes/warning setups.