Can this be done with maybe just a switch, tank, nozzle, and constant pressure pump. If so does anyone know where you could find a suitable nozzle.

ya me a a buddy each made one. used a small sprayer pump some push lock fittings a 2 way solenoid for high adn low nozzles, nozzles from snow performance, adn some relays and oil pressure switches to set start points and seems to work great well post some pics if i have time

how did you use the oil pressure switches to control the whole thing, And yes i would definitely appreciate some pictures if you have some time.

check this out http://www.turbomirage.com/water-alcohol-injection-parts-list.html

Simple water methanol base kit with all parts you need for activation of spray off a boost switch.
http://www.labontemotorsports.com/store/ccp0-prodshow/ISG-10B.html

Or diesel water methanol progressive spray system:
http://www.labontemotorsports.com/store/ccp0-prodshow/ISD-100.html

thanks exotic for that parts list. seems to be alot more involved then i originally thought.
so maybe i will go with the labonte kit its the cheapest ive seen. thanks for the great replys.