[Mike_Z4M]

I've seen similar issues on a few BMW'S with the 3.0, 2.5 engine. Thus isn't 100%, but what it possibly could be is your air hoses. From he airbox, Pcv, intake manifold. I've personally found 3 cars with this exact issue and it happened to be a leak. I replaced all three air hoses, Pcv hoses and intake manifold gaskets. Cars idled and drove great. But then again it can be a fuel issue or something completely different. IF you haven't, I recommend connecting a scan tool and seeing what codes it's throwing, that way it might guide you to the source, then post it here if you'd like so we can help better diagnose it.