That's an interesting link on your post. You are a braver man than me to be advertising specialist BMW services with a snappy
As I said above, based on what you posted it looks like a vac leak. Did you look at fuel trims or check for vac leaks?
I see one or two of these and based on that I would hazard a guess the you have a leak in the oil filler cap. Check it, or remove the plastic strap off it. Failing that look at the plastic inlet across the front of the engine.