WARNING: This page is about a different car, the 2005 BMW 645Ci and 2004 BMW 645Ci. However, it is still accessible from the selected car via links, so may be relevant.
Support exhaust system with Special Tool (31 2 220). See Fig 1. Unscrew nuts (1, 2). See Fig 2. Unscrew nut (1). See Fig 3. Unscrew hanger nuts. See Fig 4. Unfasten screws and remove reinforcement plate (1). See Fig 5. Lower exhaust system. To install, reverse removal procedure.
Fig 1: Supporting Exhaust System With Special Tool
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Fig 2: Removing Nuts
Courtesy of BMW OF NORTH AMERICA, INC.
Fig 3: Locating Nut (Left Side Shown)
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Fig 4: Removing Exhaust System Hanger Nuts
Courtesy of BMW OF NORTH AMERICA, INC.
Fig 5: Detaching Suspension On Front Muffler From Body