With the reading/research I've done, there are companies out there that make pulley kits.
Their kits seem to be changing out all the pulleys but the supercharger pulley. They still get more boost by making the crank pulley bigger.
I believe that the supercharger pulley is special and is clutch activated like an A/C system is. So...that would mean the ECU is controlling it, probably kicking it off for better mpg when its not needed.

The companies also have "kits" which have pulleys and ECU upgrades in them. Just stand alone pulleys seem to be adding 15-30 hp while the kits with ECU upgrades add more like 50 hp.

I know I'm looking to add 50 hp if I can.