According to Don Nix, a renown fuel expert, nitro does not necessarily increase power. In fact, if your engine is setup with rather high compression, adding nitro will cause predetonation (throws your prop off). Its main advantage in small amounts is to improve idle. With an engine specifically tuned for high nitro, it does give added power as nitomethene (and nitroethene) release some extra oxygen thus reducing the requirement for more air thru the carb. Use your search engine and look up Don Nix to find some extensive discussion on the use of nitromethene.