WARNING: This page is about a different car, the 2010 Audi A5, 2009 Audi A5, and 2008 Audi A5. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Checking Cylinder Head For Distortion
Courtesy of AUDI OF AMERICA, LLC
-- Check the cylinder head in several places for distortion using a straight edge and a feeler gauge.