if you have 300$ plus to spend for pullies and belt and get 3hp is it really worth it? when you could spend 300$ and get 50plus hp? for same price? you could even put a 25hp shot and its a better hp/$ than anything mentiond in this thread.
and you can even hook the nos switch to your throttle and it would only shoot nos when u are full throttle. and imo its better than f/i