I can't say I personally have used it, however MuscleCar on PowerBlock TV gained like 20 bhp (or more, I can't remember) off a water meth kit I think. One of my buddies with a GT500 installed it with an aftermarket heat exchanger and he said that no matter how hard he tries, he can't get heat soak. That was with a full track day at the local roadcourse.
Sold - Black 2000 Mustang GT, gone but definitely not forgotten
- Silver 2007 Corvette
Current - DHG 2001 Bullitt