Opening MAG weld seams and MIG brazing seams: Procedure
WARNING: This page is about a different car, the 2013 BMW 550i GT, 2012 BMW 550i GT, 2011 BMW 550i GT, and 2010 BMW 550i GT. However, it is still accessible from the selected car via links, so may be relevant.
Grind off weld seams with a belt or angle grinder. Do not grind the base material thin.
Use a chisel to separate the sheet metal flange and remove the component.