Getting back on topic...
OP the noise you're hearing is likely the solenoid for the injection pump on the fuel rail. Interestingly the acoustic cover on the engine does not cover the pump, so you get that clickity-clack at idle. I learned recently that some cars were built without a sound dampener. It might be worth while to take the car to the dealer and ask them to visually inspect the pump and make sure the sound dampener is there. A friend is a master tech at a local BMW dealership and he had a customer car in the shop without the dampener. He reported a slight improvement in sound with it installed.
http://realoem.com/bmw/showparts.do?...16&hg=13&fg=15
I am referring to parts 9-11 on the diagram.