Call www.superchargersonline.com - Let Tony know that Rick from Fast Intentions sent you. Get the ENTIRE $40 FMU disc kit - not just a single disc. Until you take the FMU apart, you wont know which disc you have installed. They have ranged from 7:1 and 8:1 - which is supposed to be standard...though MY FMU had the 10:1 in it from the start, the largest is the 12:1.

Ideally, you want to install the pulley and then tune and see where you are. Depending on your ratios, you'll choose which disc based on the FMU disc factory installed. The kit also comes with a new diaphragm.

Rick