You should replace all bushings/ shocks if you want your SL to ride like new. It will cost some $$ but it is well worth it. Notable the Subframe bushings will cause that noise. Just check all bushings and replace even if they are still notable "good"

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2001 E55

2001 E320 Sedan

2001 Subaru Legacy

2006 SLK280

2016 Subaru Outback 3.6