Is this one to aviod?
 

Here
QUOTE...he ONLY issues worth mentioning are; as with most KV6 engines it suffers an occasional rattle from the variable valves, depending on weather/heat of the engine/revs etc, this is purely only a cosmetic/audible issue and I actually purchased the vehicle with this sound as I knew the engines were prone to it and it has never bothered me and certainly doesent effect performance!

The rattle is more likely to be the purge valve.

Sounds like the inlet plenum

http://www.pistonheads.com/gassing/topic.asp?t=921250

reckon he will take £650 cash, with the belts done and all the new bits might be worth a look, now the rattles can go on for a bit before it needs doing. Always ebay for another one and take a gamble.

EDIT Or the purge valve as Pete says. :-)