Sure SOUNDS like something loose...???
Maybe re-check the torque?
Especially the center nuts at the tops of the struts and the nuts at the tops of the shocks. DO NOT Over-tighten them, but you might make sure that they are to spec with a torque wrench.
Those particular nuts may not allow for free movement by hand, but may have an impact when the car is settled and moving.
I had something similar once with one of my front strut bolts.
BEWARE, the Center nut takes a decent bit of torque, but if you over-torque one of the 3 bolts that hold the strut in the tower, they are KNOWN to Shear at Very Low Torque.
Do NOT Over-Tighten them!
Keep us posted.
