Maniac. There are systems like what your talking about that do it for you automatically. I cant remember the name of the company but they do crazy swaps of things like 1600hp rx7s and shit that is streetable. They have a 2 tank system just like what you talking about and when the car hits over a certain amount of boost it switches the tank automatically and runs the race fuel mix.
http://www.youtube.com/watch?v=AmACTP69Zh0