methanol , alc/water injection - takes heat out of the air going into the engine... it'* injected into the intake pipe. the benefits are removing detonating heat levels and also adding a 'fuel' at the same time. it'* not like nitrous which gives you an actual hp boost. alc/water and meth injection just let you run higher compression with nasty advanced timing, or more boost , etc.
only thing better then a meth or water/alc injection setup for this purpose is Propane injection (I love propane injection)
I've heard of turbo buick guys hooking up alc/water kits set to run @ a set psi level and also @ a set KR
I've been looking into DIY a/f and KR meters and possible making up a bunch as "prizes" for the next westcoast bonne meet
Check out this site for a great "what it does" and a full "DIY how to" http://www.dawesdevices.com/water.html