I bought the aftermarket smaller pulley from Alpine for extra boost. It was ~$80. Turns out the pulley diameter is only 2mm smaller than the original, and I really couldn't feel much difference in accelleration. I then had the new pulley machined another 1mm. Maybe a slight improvement in accelleration, but abysmal gas mileage at 13-16. I'm also a little concerned about the transmission's ability to handle the extra torque. I haven't had it back on the dyno, mostly because I was so disappointed with the numbers from the original S/C.