Should be Bosch Platinum for a facelift S8 (unless there are some new better ones that replaced them recently?)
FGR6KQE
101000054AD
They should look like this:
http://forum.a8parts.co.uk/showthread.php?t=8275
If I remember correctly several good independents recommend these OEM plugs too,
some other makes like NGK may run hot. Hope I'm not spreading any bad rumours.