Another vote here for a water/meth set-up
. By adding a good quality water/meth set-up you'll be able to add more timing, lean out AFR's, and possibly run more boost if you changed your pulley.
Also, if you run this set-up you will NOT need to add larger injectors, different fuel pumps, etc. We usually see injector duty cycles drop substantially by adding water/meth.
One piece of advise.....spend the extra money on a good quality system like Aquamist, as it has built in fail safes. If the Aquamist system senses that it is empty or not providing consistent pressure (ie: hard cornering, etc) it will activate a kill switch. On turbocharged cars like GTR's, Evo's, and STI's this system will cut boost immediately. Since a supercharger's boost is controlled by pulley size, rather than an ECU I'm not sure how it would work with your set-up. Perhaps Lemans Blue can chime in here
.