Hi all, long shot but but was underneath my a6 c6 2009 today, doing a cambelt. I noticed a a heavily corroded part above the l/h side of the steering rack. Looks like some sort of possible filter housing? Alloy body with a black plastic cap. Possibly bolted / mounted to the steering rack? I forgot to look into it before I left (cars round a mates) hoping to get down there tomorrow but does anyone have any idea of what it could be?

It's a UK model. R/h drive. 2.0l diesel engine. Engine code CAG. any help would be appreciated

Joe