Used slightly different verbage in the search and dug this one up...

http://www.peachparts.com/shopforum/showthread.php?t=6755&highlight=1st+slip

"Good chance for a simple problem here; you probably have a bad seal or broken piston on the B1 band. It can be removed from the outside and MB has redesigned the piston so a complete assy should be installed (it has a much broader teflon seal)."

"I knew I had something a little wrong here. The problem is right but the band is actually B2. The piston # is 107 270 04 32. It lists for $89."

In addition to the normal vacuum adjustments and whatnot, it seems like that would be the next culprit. This forum is quite nice! Much better than the useless VW forums! "Dubs are kool d00d" seems to summarize most VW posts I still think the Miata forums are the best though.

Thanks,
Ray Ackley