I used a AIS kit (
http://www.alcoholinjectionsystems.com/) on a procharged engine that I just built (I know you are asking about NA) but anyway I was a bit worried and was not sure I believed the hype... I tell you what, we tuned the engine on 91 octane with 14psi and it made 890 hp (may have been a little less) well the tune was happy so we just for giggles put the AIS kit on the engine on the next pull with the same tune made 934 hp... I was real surprised and impressed... I will say this, it has me seriously thinking about going that route with my engine.. If you have any questions call AIS the guys name is Rodney but plan on being on the phone for a while as he is willing to explain everything in depth with you and he will more than likely have lots of questions about your set up..
Chad