hi,
i recently bought a 2000 V70 w 120k miles, most everything about it seems good for its age & milage.
after a couple long vacation drives this summer i noticed what sounds like brake booster vacuum leak or whine. when i start and/or shut off the engine and sometimes while inside the car while driving i hear a related or similar moan/whine when the A/C cycles with the AUT setting on the climate control.
im pretty familiar with my older '95 850 wagon but the few places i have looked/checked for a worn or leaking something-or-other i haven't found it yet... i felt certain it was brake booster leak but... now im not so sure
any suggestions/guesses on where else to check?

also, i have heard the AWD can be a problem as it ages, what should i look for with that?