Im having the same problem at the moment. Rattle on startup and when it hits about 1800 rpm, when you rev it when cold it is quite bad but goes a little when warm.
Having new camchain and camchain adjustor, plus 20 new tappets and oil pump and pick up feed....should purrr like a kitten after that little lot. Also you may want to think about changing oil pump and pick up pipe, this is probably knackered/blocked which has caused the hydraulics on the camchain adjustor to fail....hence the ratlle!
Costing quite a bit, alot more than £400, probably around that for just the adjustor..... audi wanted £350 just for the part...tappets alone are £200. Im having the lot done at stealth racing vw audi specialists near leamington spa, good bunch of lads...know their stuff.