[f5fstop]

What we cannot determine is that your groan and my groan are the same. My groan actually started to turn into more of a metallic sound. The main reason GM is taking mine out in the service garage is to make sure nothing it tinkered with, and the entire unit, with fluid is sent to BW for teardown by their tech in their research lap.
I never felt anything in the brake pedel, but I heard this sound only when doing a heavy braking.
I guess time will tell, as of right now, it is still sitting in the garage and waiting for a new case.