One of our local club members runs his own shop and put an e30 m20 flywheel in his e36 m50. Here's a post which recollects most of what I remember him saying about the swap:
http://www.bimmer.info/forum/showpos...15&postcount=7
He did say it made a night & day difference getting rid of the dual-mass boat anchor flywheel and it picked up gobs of power on the lowend.