#1 There are those kits that come on and spray the same amount of water regardless of how much boost is run.
#2 There are those that increase water spray pressure based on increased boost.
#3 There are those that are (sp) controlled by tuner input.
#1 is like the ebay systems and Stage 1 packages of some better known systems: Boost hits a set point the spray begins. #2 is like what you get with an SMC system: Boost hits a set point, spray begins and spray pressure increases as boost increases to a set higher point. #3 is what you get with a Stage II Coolmist system (and maybe a Hydramist): It's plugged into a computer and spray can be custom regulated at various points.
For me, #1 is a no go. #2 is what I was about to buy...an SMC kit to be precise, but the local shop didn't have one in stock and after a little research it appears getting a kit from a place that doesn't have it in stock will take a long time and SMC customer service isn't very responsive. [I don't know firsthand if that is true.] This lead me to looking at the Coolmist Stage 2 which I can get cheaper than the SMC and it's more controllable. The question is, is that much control really necessary? I know what the SMC kit is capable of and the control box has better aesthetics (sp) for in-view mounting. You can howerever control the Coolmist in the same manner as the SMC kit.., i.e. in cabin without computer. Part of my attractions to the SMC kit is that its very simple and uses the ww tank and replaces it with a smaller one. To do the same with the Coolmist would require some custom work.