Does anyone have a diagram where they go?
might be Similar to this : 'Layout of vacuum hoses ( bmw ) M47'
BMW TIS - 11 74 ... Layout of vacuum hoses (M47 / M57TU)
in that the Vacuum tank looks the same
( i've no idea what the pressure converters are on that )
there will be something connecting the vacuum pump to the v.tank ( i'm assuming )
from the tank .. there will be branches out to
egr unit / solenoid
turbo vanes unit / solenoid
( i think that's all .. can't think of anything else right this moment .. might be wrong )
( googling didn't display any diagrams except that one .. on initial search)
no doubt it might be a right job finding the leak ..
Also since I did the EGR bypass Ive always had the buzzing duck noise (mentioned on this forum a few times) That noise has never bothered me, but since the garage had my car the buzzing duck noise has been greatly reduced to a very faint sound making me think vacuum pressure has been reduced.
score 1 for the 'duck' .. as an indicator of vacuum system health .. or lack of :-)
best of luck tracing the fault ..