FYI- should have alignment checked since you have lowered the vehicle.

Sounds as though you have eliminated balancing as a possibility though it is not unusual that a vibration in a particular speed range is a balancing issue.

I would say it is time to have the front suspension thoroughly checked over.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas