i havent done too much research into the setup, but last night i was looking at a thread on here and someone mentioned that they had heard too many horror stories to use a crank underdrive pulley. what all issues have any of yall had or heard? this was to be my next upgrade, but if it is going to be more trouble then it is worth i will look another route

 

They're not dampened for starters -- Also the pulley key can strip if it's not reinforced. Both can mess your crank up pretty bad. Just stick with oem...

 

you may not experience any problems for a while (if they do cause problems). But I'm staying away from them for my Z.

Here's some good read:
http://www.atiperformanceproducts.co.../101/index.htm
http://www.dinancars.com/bmw/technia...armonic-damper
http://www.suprasonic.org/public_htm...atedamper.html

The choice is yours.