There is a dyno difference with the UR pulleys, depending on the model of the car. You'll gain some hp and torque out of having pulleys, there's not drawbacks, only gains all the way across. I gained around 5whp with just the Underdrive Crank Pulley. I bet they'd work best with Superchargers. I recently bought a p/s pulley, all i need is an alternator pulley and i complete my set. They're nice under the hood too.