[Jon@MagnaCharger]

Also if I want to run an ATI under drive damper what size of pulley would I need to run again 8lbs of boost.

Whatever you do, don't run an "underdrive pulley." This will spin your supercharger slower and result in boost loss. If you want to run an ATI damper, then make sure it is an "overdrive" damper. This will spin the supercharger faster without having to go smaller on the supercharger pulley - resulting in more boost with less chance of belt slip.