best system i've seen with fail safes are the aquamist kits
you can install the kit yourself with a friend - the hardest part would be to select the area you're tapping the nozzle for the wami
most people tune with a 50/50 water meth mix to get best results
octane rating may be hard to determine without knowing size of nozzle, flow rate or how the kit comes on - progressive etc...
teknet has systems from coolingmist - you can look into that as well
http://www.aquamist.co.uk/vbulletin/sho ... php?t=1936^install on an sti
http://www.coolingmist.com/^coolingmist