[NewArt]

This is my opinion based on my research and my personal experience:
An underdrive pulley is vey useful for those of us who drive their cars on the track where 90% of the time the motor is in the 4000 rpm and up range. It helps us avoid cooking the peripherals (a/c, power steering, alternator). It does not increase the horsepower or the torque. If you disagree, show me the proof. If you are not tracking, put your money elsewhere.
Oh, btw, the rss is a good choice.