It is important to note that this design is specifically tailored to reducing vibration. Weistec explains it best, "Every time your engine fires a cylinder’s combustion charge, pulses of torsional vibration are transferred into the crank shaft. These vibrations can become exponentially violent as engine rpm is increased. To dampen these destructive vibrations, the outer housing turns at engine RPM, while the inner inertia mass immediately self-centers and is free to be pulsed by each combustion event. As the inner inertia ring advances and retards itself in relation to the outer housing, the Mu (friction) force through the inertial system transforms the vibrations to heat, which rapidly dissipates through the internal fluid and housing."
So what are the options? Weistec offers three supercharger ring diameters. 150mm is the stock size and can be used with the Weistec M113K 3.0 liter blower upgrade. There is also a 170mm and 180mm ring which also can be used with the stock or upgraded supercharger. The 170mm pulley overdrives the OEM blower by 13.% and the 180mm pulley overdrives it by 20%. Anything further than this and you will see diminishing returns as the blower is spun out of its efficiency range meaning it is time to ditch the factory 2.1 liter.
Pricing is $1249.99. Specs and applications along with a dyno graph featuring the 180mm pulley below. Keep in mind you will want to tune for more boost, Weistec's ECU upgrade is here: http://www.weistec.com/m113kecu.html