Hi,
With VCDS you can set the volume in the A9 Controller as a percentage. When I did the change, I was in ECO mode and it was set to 100%, so I reduced it to 0% and that appears to work OK (ie, it stays quiet no matter what mode you select). Some of the guys on the R forum with post BW22 cars appear to have a option to allow adjustment from the config menu so I'm hoping to find that in the 09 controller adaptations list and expose it with VCDS - I just need to get a full map of the controller to try and suss it out.
Neil.