Its common because of the condensation that builds up with the cooling temps. The boost gauge is attached to the engine by way of a vacume hose.
The Exhaust has the same type of condensation build up too.
I've known a few people that have installed Filters from fish tanks to stop the needle vibration while at vacume. Wonder if it would help the condesation too.
I've got a VDO also and have this same problem But I'm not concerned about it as my car sits in a garage a lot.