My bad that *is* the (anti) sway bar.

What you have labeled as the sway bar is the anti sway link. The sway bar aka stabilizer is the thick staple shaped bar that is connected via links up to the strut.

Reviewing the photo it looks like the bolt for the lower arm is loose. It also looks like the tension bar is new which would make it less likely that's the problem but I would suspect it anyhow.

Thunk in the trunk as mentioned could be the rear subframe but if that is loose you should hear small thunks when under power and hitting small bumps

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)