fizix 101 - you'll have to look long and hard for something that gives the cooling subsystem (in this context, the air charge cooling subsystem) a greater specific heat capacity than straight water.
as far as i know, the additives like the one listed above and redline water wetter are simply surfactants, which make me wonder if a couple of drops of dish soap wouldnt accomplish the same thing.
i'd run straight distilled water with a little bit of antifreeze in it for the corrosion protection additives. but thats me. im weird.
try the stuff referenced in the link out. if it works enough to make you satisifed, relative to the money you spent on it, then go for it. please post your results. what works for me might not work for you. find out what works best for you.