Virtually all these 20yr old BMWs will benefit from a smoke test...So yes go get a smoke test, preferably by someone who knows the M54 engine. There are like a dozen possible sources of a vacuum leak.

__________________
'03 530i - manual swapped - 425k miles
'06 325Cic auto 115k
'05 X5 3.0 auto 158k
'99 E39 528i 5-speed 130k