Here is a better video of the sound (it came back).
Have to book it in
As you can hear if you listen right to the end it just goes away suddenly. I did not do anything to make it go awat.
I feel like its something in the exhuast hitting the under body or vibrating or the damper not working properly but I'm confident it is exhaust related.
It was doing the noise pretty consistently and I switching the modes from sport (i.e. exhaust values open) to comfort and the noise went away instantly when changed mode to comfort.
It's only at idle. Tends to happy more on slight hills.