Bmw sheet metal at the top of the rear shock towers in E30, E36 and E46 are a well-know weak point. The metal tends to tear over time, especialy if stiffer shocks or coilovers are used. Made from 3mm thick steel, CAD designed and precision CNC plasma cut right here in Greece. They can be welded in or used as-is. 

Bmw E30/E36/E46 Rear Shock Reinforcements