Suspension feels tight but have you checked if all the nut and bolts are tight from when the work was done on the front suspension?

If it doesn't vibrate under hard acceleration from a standing start until you get to 50 and it stops at 80 are you always in the same gear and are you still under hard acceleration at 80 when it stops?

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