put it to ya like this
in a talon tsi i had a couple years back. i had water injection on it. 180k miles on original motor, 24 psi on stock ported 14b, a ported manifold, hard pipe kit, k&n filter, modded mas air, 3 inch turbo back exhaust pulled a nice 108 mph. for less then 500 bucks in mods. now the 24 psi was on 110 octane. im a HUGE FAN of water injection. it gave me a chance to run silly amounts of timing {close to 30 degrees under full boost} at this boost level. i can go into more detail if need be. but this should give you a good idea on what water injection can do. if it can do that on a high mileage turbo motor, imagine what you could do on a fresh L series!
as far as your problem. stock efi systems compensate for cooler air, standalones do not. {at least the ones im used to messin with} so. with the Ms system, im not sure if you can do multiple maps, like for warm temps, medium temps, race gas, pump piss, cold, or something of that sort