WARNING: This page is about a different car, the 2014 Audi A8 Quattro, 2013 Audi A8, and 2012 Audi A8. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Identifying Engine Cover, Removal
Courtesy of AUDI OF AMERICA, LLC
-- Carefully remove the engine cover from the 4 fasteners -arrow- one after the other. Do not remove the engine cover on one side or in a jerking manner.