[Vwdiesel] Turbo trouble?

[Dave Heart]

Have been using 85Jetta TD engine in 81pickup. Now getting a loud noise at 
idle which seems to come from air filter. Not injector noise. Sounds very 
loud; like a paint compressor. A pumping sound. Turbo boost seems to be ok. 
Ideas?

Also, the aftermarket cone type air filter has branch hoses with 2 valves 
and wire connector plugs which are not currently connected. One is a large 
round type  mounted on the  intake and the other smaller one goes to the 
valve cover. Do these valves need to be wired to something? Can they cause 
trouble?

Thanks, Milton.