thanks for your reply. here is the best picture I can take (it gets tricky angling the camera that far into the wheel)



thanks to you guys, I'm almost 100% certain that the mystery part is the sway bar.

it looks pretty corroded & rusted.. there also looks to be a hole protruding through which worries me.

the 2 other smaller arm pieces that connect this black bar to wheel look to be in fine shape.

would you guys recommend replacing this rear sway bar before something goes very wrong?

thanks for all your time! :-) -Matthew