I installed the Go Fast Bits pulley set yesturday. It's a 3 pulley set and comes with new belts. All three pulleys are smaller in diameter than stock, but spin everything (except the a/c)at the same speed. The motor seems to rev alot quicker now with no hesitation. I paid $219 for mine from www.vividracing.com
Not sure about the a/c, it was cold last night and this morning. I guess it will spin the a/c compressor slower because the crank pulley is smaller. We shall see this summer.