vibration on deceleration?

[doitover]

My 318is is almost running the way I would like, except for one thing.
When I take my foot off the case there is a vibration that is kind of like what a worn u-joint would make. All of the rubber on the car looks good so before I start shot gunning things, what sorts of things on these cars are known to cause vibration on deceleration?

[DesktopDave]

Your guibo looks good?  You've eliminated the mounts, so I'd check for play in the drive shaft or half shafts.

I'd also check the diff, they don't last forever and it'll grumble as they wear out.  Might be a good diff with a bad bearing...shouldn't be very expensive to fix (or get that diff upgrade you've always wanted).  Check the seals and oil level on that first, it's easy to get to.