Rattle inside a black box connected to the engine .

the only thing that this might be is the "intake manifold runner valve adjuster" which diverts the intake air, sort of like intake tuning. still would advise that you run it by your usual BMW shop and they can confirm this. may be something really important, then maybe not. small noises have a way of turning into big expensive noises!

Did you ever find what the cause of this rattle was?? I have the same issue in my 2004 530i. Thanks