I fitted lowering springs myself, so do you know what exactly wasn't tightened down?For me this turned out to be loose mounting hardware for the rear coilovers. The shop that did the install of my new coilovers forgot to tighten them down all the way. If any suspension work has been done, this is the best place to start looking.
I've been bothered by a very similar sounding noise coming from the rear hatch area too. I believe its the metal shroud above the muffler area too... There's so many places where its metal on metal.Has anyone found the cause of this metallic sound? I have personally invested a lot of time trying to solving this issue as mine does the same. Its mainly on uneven surfaces like backing out of my driveway and is most noticeable when cold. I'm starting to think its the heat shield above the muffler.