The concept is very real... Whether it would net 70 hp or not is another question..

http://www.nitrousexpress.com/Pages/Ntercooler.htm

I intend to build something similar.. the kits out there are just too expensive for what they do.. It's so simple a concept that I could build a nice looking and good performing one w/ readily available stuff.

A bottle full of Co2 would DRASTICALLY reduce charge temp, ESPECIALLY at roadway speed w/ the air hitting it after being doused in gaseous Co2.. Basically, it would likely be cold enough for ice to form on the intercooler.