~Just get a co2 regulator to drop the psi down to like 150 coming out of the bottle.. u can get this off ebay by searching for welding supplies or a kegerator they are like $15 for one that handles 4000psi and can drop it to like 1psi
~An electronic solenoid for an airhorn and connect it to a switch in the car $3 if that.. (when u hit second gear hit the switch and just spray the intercooler with freezing cold co2 the rest of the way down the track. when you finish turn it off)
~some thin copper tube and drill small holes in it for the sprayer itself..
~get a co2 tank filled.. connect it all together with some cheap vacuum line and its done.