Now I guess I have further confirmed the diagnosis of rear shock mounts. The parts are on their way anyhow, but while noodling around yesterday, looking for trouble under the rear end, I found some.

One of the trailing arm bushings is shot - the metal can around the rubber pulled away from the cast steel. Actually, it's what FCPEuro calls "trailing arm bushing", but I'm not sure it is the right name. Maybe "delta link arm bushing". Anyhow, I'm going to start another thread on that repair.

But I hammered a couple of wooden stakes into the space where this bushing can separated, to keep that end of the left hand trailing arm (delta link arm?)(which is actually on the right side of the car) from moving. So where it used to be held by the bushing, it can't wobble around and bang - in case that was what I've been hearing.

Then took it for a drive down the very bumpy part of my street. The big cans of tomato sauce were still banging around inside the rear spring tower. Brakes on or off made no difference. Seems like the trailing arm bushing wasn't the noise.