on the '06 it probably still has a one piece step shim. sooo... with a new belt measure the exact belt to sheave clearance. take your number minus it by what.... 0.020" is a good belt to sheave clearance. then minus the two.
on the step shim there is a small side and a big side. you will have to take it to a machine shop and get your fiqured number machined off. then when you put it back in you should have your 0.020" clearance.
you could buy the clutch holder tool, spider nut socket, spider removal tool. if you are only going to take it apart once just measure things up and take it to the dealer to take apart and put together.
if you going to go ahead with the tools then you need good size torch... butane works fine. and a 1/2" strong arm with 3' snipe. and a real sturdy vise bolted to a sturdy bench. have to heat the spider on the flat part... for a couple minutes to loosen the loctite. then remove the spider nut and using your 3' snipe try to but loose the spider. make to clean the threads on everything prior to reassembly.
when reinstalling use loctite... i think the green stuff (i never had a problem with blue 242) torque the spider in the area of 250-300 ft/lbs. install the nut and tighten.
on my '08 m8 i was expecting the step shim but low and behold... just regular flat shims in there.