Shouldn't have any valve train noise, but the chain can put out a 'whine'.But if its clattering away then you most likely have some kind of issue, like low oil pressure or worn out chain components maybe.
Mine's quiet as a mouse. Exhaust buzzes a bit.
What is the mileage? I have a feeling the guides are just worn out or the lifters are getting weak. Mine has over 150k...
81k. If the guides are that worn out, I'd do a chain/guide replacement before the engine grenades.
I am looking for a lower mileage one anyway...
150k isn't really high mileage for a BMW engine. As long as nothing else is wrong with it, I think I'd just replace the worn parts.