About your noise!!!
Reading your post and trying to Imagine you noises..MB has a Plastic connecting rod that mounts on each side .. It connects to the sway bar on one end and to your rear break plate.. look under your car there is one on each side..they are fairly easy to change and not very expensive either...... when new they will be a off white color or grey. Most of the time it will be that knocking ..hollow sound you are hearing....... Let us know what you find.............Pete GABBYS MB REPAIR