Check your intake bellows and elbow directly behind your air box (in between the air box and firewall, on the drivers side of the car). Take off your air box completely and inspect the elbow and lower bellows for any cracks that may have developed. If they are the original rubber components, I would replace them anyway because they do not last long.
There aren't a ton of vacuum lines (I am not too sure how many there are exactly), but I do know that just replacing them all will be way more expensive than the $150 smoke test. There are most likely shops around that will do it for half that price also. There is a shop around me that does them for $85.
BMWCCA Member# 451235
(Summer) 2001 330Ci - ZSP
(Winter) 1994 530i "Greenie" - PARTING OUT! (PM for details)
(Grocery Getter) 2002 525iT