[2001 ZTS]

There are lots of spray kits out there now I saw one where there is resevoir that looks like a back pack for the drivers seat.

Lots of turbo timers/boost gauges these days have spray activation functions.

There is a LED gauge out now that shows air temp before the air hits the IC and after the passing over.

It is something I'll do eventually since it is just a matter of a few STi parts for me. I already have a spray controller built into my ECU monitor. I haven't looked into it much but am pretty sure the set point uses boost P not RPM or anything else.