WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: View Of Exhaust Outlet Inspection Areas
Courtesy of GENERAL MOTORS CORP.
Clean the exhaust outlet.
Clean the exhaust outlet mating surfaces.
Inspect the exhaust outlet for dents or cracks.
Replace the exhaust outlet if any damage is found.