There are alot out there but I ran the cooling Mist single stage kit and it worked great!!! never had a problem and its a affordable price. I was able to run 30PSI on a GT35R on 9:5:1 compression on pump gas without even comming close to my knock threshhold. I even ran 50%water and 50% alchohol which I get from Home Depot(its 100% denatured Alchohol with a dab of meth put in it so people can drink it. cost like $10 for 1.5 gal's which laster me 5-6 fill-ups when mixed with water. Water Injection, Methanol Injection, Alcohol Injection Systems | Coolingmist