supercharger info

has anyone changed the pulley on the supercharger on a 2001 frontier? if so how was the effect on power? and i read somewhere that there is a "bypass" valve on the supercharger to conserve fuel. if this is true, is there a way to omitt this "bypass" valve? it is supossed to help on fuel consumption. Hell is i wanted a truck for "fuel consumption" i would have bought a four banger.