Yeah my money would be on tension arms. I just put a set of Febi on, I expect them to last 40K miles. Be sure to replace the one-time-use fasteners. The torque spec is important to achieve proper bolt stretch. Found in TIS.

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2009 E70 N62 Titansilber Sport
2000 E38 M62 Schwartz II Sport
1997 E36/5 Schwartz II M-Sport (gone)