i am in love with my e39 540
and i have it since 2 years
i faced too many problems since that time but driving her majesty didnt allow me to surrender
the solution for your issue is too easy, it is all about leaking air, all you have to do is to change the following :
BMW E38 Intake Manifold 1995-2001 (OEM) and make sure you buy the original ones and in the same place where this manifold is located there is two aluminium tubes, one of these tubes is also for air intake make sure its no leaking also
take care of your 540 she will take care of you
