I forgot to answer your second question ...

Think of your pulleys like the sprockets on your old 10-speed bike (27-speed, etc). The crankshaft pulley is the DRIVE pulley (like the sprocket attached to your pedal/crank assy). When you shift to a bigger front (drive) sprocket the rear wheel turns faster. The supercharger pulley (and ALL accessory pulleys like the alt, water pump, etc) is a DRIVEN pulley (like sprockets on the back wheel of your 10-speed bike). Switch to a smaller SC pulley , like shifting to a smaller sprocket on the rear wheel of your ten-speed... the supercharger/wheel spins faster.

The effect (in terms of PSI) that changing a pulley size creates is predictable. Decrease your SC pulley by x percent (or increase your crank pulley by x percent) and the volume of air being forced into the motor increases essentially by that same percentage. However, you must keep in mind that at 15psi (stockish boost level for an srt6) the SC is actually moving the equivalent of 29.7 psi (15 psi gauge plus ambient air pressure of 14.7 psi). So, for example, if X is a 10 percent increase in crank pulley size (or decrease in sc pulley size) , Your stock 15 psi does not merely go up to 16.5 psi ... it goes up to 17.97 psi. The math goes like this .... 15 psi + 14.7 PSI = 29.7 psia(PSI absolute) ...10 percent of that is 2.97 which is your gain and gets added to your original 15psig (PSI gauge) for a new total of 17.97 psig (referred to commonly as merely PSI this is the number you see on your boost gauge).

hope that helps,
Chris