Dont' pay Audi's extortionate price of £26 for a new filter. Don't even pay Halfords' price of £13.50 for one, assuming they've got one in stock or, failing that, can get one in.
Take the old one out (easier than ever in the B6), put it n a sinkful of hot water laced with washing powder, leave it to soak for an hour. Then clean out the crud (& there'll be lots of it!) with an old toothbrush, refresh the water & washing powder and leave it to soak another hour.
After that, rinse it off in clean hot water, & stick it on top of the boiler to dry.
Good as new, and a few quid saved.