Ok, so I am positive that it is coming from the ABS/ASR pump. It makes a clicking noise as if the pump needs to be oiled or lubed in some way. I'm not sure why its doing this or what effect his has on the ABS/ASR systems as they both seem to be functioning properly - i've tested them As I said earlier, neither the ABS or ASR dummy lights are on and the pump only seems to do it a few random times while driving (ie. I can not reproduce the noise by doing anything)

On a related issue, how (or does it at all) does the ABS pump interact with the ASR system. Looking at other e320's:


This e320 is without ASR and seems to have a "normal" sized ABS pump (common to many other w201/w124 cars)

My pump/unit on the other hand is enormous compared to that one (seen here for sale on ebay for 275):



and here on a wagon w/ASR: