After changing all the suspension components front and back, my car
now will have a loud "bang" after going over a hump or a large poth
hole. It sounded as if the absorber is being stretched to the max and
knock at the end of the travel. How is the possible? I'm using a set
of brand new Bilstein HD. Ive check and can confirm that the absorber
is of the right specification. Before the suspension job, the bang
comes from the left front. After those extensive work, both front and
rear is making the bang.

here is the items i ve changed: all done at the same time by the same shop.

Tie Rods
Drag Link
Front and Rear Absorbers
Rear Spring
Front and Rear Spring Buffer (4 dots for front and 3 dots for rear)
Upper Control Arm
Lower Ball Joint
Guide Rod Mount
Guide Rod-Lower Control Arm Mount
Idler Arm Repair Kit
Lower Control Arm Bushes
Steering Absorber
Rear Sub Frame Mount
Rear Trailing Arm Bushes
Rear Differential Mount
Front Sway Bar Bushes
Rear Sway Bar Bushes
Rear Sway Bar Link