Somewhere in this section i read that a few people believe/know that an underdrive pully in a FI condition will render a "loss" in performance or power. My question is does this theory or fact apply its same principles when one uses n2o?

 

Only applies to a S/C which releys on the belt to make it work. If you underdrive the pulley, the belt spins slower. Resulting in a blower not spinning up to its normal rpms.
It should give gains on any turbo or N20 car though.

 

Definetely helps on a turbo and n2o setup. Ive had it on for a long time. Soon to combine it with the fidanza flywheel.

 

That's partially correct...there are stock size pulleys that weigh less, so that wouldn't have a difference in the S/C setup...