I see all these AEM pulley kits online. My question is what do they do, and do they increase power. I know one of the is I think for the crank. Are the others a/c pulleys or what? I have a 2000 civic ex. D16y8 motor. Is it worth buying that for my car.

 

they lessen the rotating mass of the crank, kind of the same pricipal as a light weight fly wheel, unless your running out of things to do to your car, i wouldn't, save for a swap or turbo.