OK i was thinking the other day, if water injection increases the density of the air, wouldnt adding a few ice cubes in a special container allow cool damp air to be available? Youde have to replace the ice often, but would it have any effect?

Racers often do this as the track, its called a slush box. Some use this trick to cool the fuel as well. Not real practical for driving around but ok for 1/4 mile spurts. Watch how you set it up as you dont want to suck in water and hydro lock your motor.

Pdad is right. Anyone who is even remotely interested in Water Injection better do their homework first. It can be a very dangerous thing, and it'* not nearly as simple as it sounds. In your case with a 90 SSE, it won't benefit you much. A slush box wouldn't gain you 5hp. Water injection is of more benefit on forced induction cars. Compressing air creates heat. Heat cause detonation and KR. You don't have that problem.