Hi, I changed the chain and rails. The old chain was in perfect condition(5mm longer than the new one). The guides had 1mm wear on chain surface on some places. There is one screw that is holding the plastic rail for the block, it showed a lot of wear and the hole in the rail had some wear too. The screw has updated bmw part number and the price is 4 euro. It is situated behind the hook for lifting the engine and can be changed through a hole closed with metal cap. No need to open engine. I recommend this to all owners with cars over 200k km. Mine has 230k. The other fixing elements showed no wear. I thing mu noise could be from unwanted play of the guide rail because of this part.