Can anyone tell me what this part is andwhat it does?

It's mounted on the airbox and has one tube going into the wing alongside and it has another tube going down behind the engine. It is run by a little electrical connector and it's wiring runs up with the airflow meter wires and splays off.

It is making a loud clicking sound which you can hear clearly in the cabin. It's as loud as a typewriter but if you fiddle with the connnection, the noise goes away.

EDIT:
ps, ignore my sig., I now have a '98 A6 2.8Q Sport with 109k