I've seen guys run it to prevent the motor from melting. It works for that.
I haven't seen a dyno sheet backing up power numbers on anybody's water/meth kit though.
I saw a truck loose 20 HP on a dyno though, by turnin on his 40%.
I'd really like to hear that these will add power, but I think that IOT see power out of 'em, your EGT's must be up there, or you're runnin alot of meth.