Sorry pressed wrong button. READ THIS
Spoke to my BMW dealer yesterday. Long story short.
The pushrods had to be replaced on my car, 2008 528i (9840 miles on it) because the pushrods were manufactured poorly! So if you should hear any engine tapping, at cold start or anytime for that matter, the reason could be or is that your pushrods are faulty.
The E60 engine uses rocker arms, now called Roller Drag Levers and overhead cams. The cam lobe actuates the pushrods which pushes the rocker arm which opens the valves.
When the pushrods don't work properly the valves stick and thus, the tapping sound from the engine. This can rob you of power and performance if not attended to.