The few guys that I know of who have alum. drive shafts for the mkII were custom done. One was a 1-pice drive shaft, so he had to pull the rear end to install it. The other guy got a 2-piece. Both said that they noticed a little difference in acceleration, but not much. If you want to rev faster get an alum. flywheel - this will reduce the ammount of rotational mass at a point that is far away from the center of rotation. A steel driveshaft, while heavy, imparts little resistance to spin-up b/c all of its mass is so close to the center of rotation.