WARNING: This page is about a different car, the 2008 BMW 760Li, 2007 BMW 760Li, and 2006 BMW 760Li. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Pliers (11 9 500)
Courtesy of BMW OF NORTH AMERICA, INC.
NOTE:
For mounting pistons in engine block - 92 mm dia.