If you have a mechanical boost gauge, even the best ones can rattle under certain rpm / load conditions. It happens because of the minute pressure fluctations that occur in the intake manifold when the intake valves open. The common solution is to add an inline vacuum restrictor (see image below). You should be able to pick this up from any auto store. Sometimes this doesn’t get rid of all the noise though. The key is proper placement. I picked this tip up in the MKV forums from the someone with the username Plac.
The inline restrictor has one end that is clear while the other end contains a brass piece with a small hole in it. This dampens the movement of air in the boost line. Place the end with the brass restriction about 5-6 inches from your boost tap facing the intake manifold. This should get most of the noise/vibration.
I’ve had this restrictor in for quite some time (along with a miniature fuel filter to help quiet things down even more) but I would still get vibration under certain load conditions. I simply moved it according to this tip and it is silent for all intents and purposes. I haven’t heard the gauge rattle since moving the restrictor. Hope this helps you as well!