I can certainly tell the car is "louder" in S mode, as the revs noticeably increase when moving from D to S.
However are the flaps definitely not all open when driving in Race + D?
The trouble I find with S mode is that it holds 2nd gear too much when cruising around town, so I often drop it back into D.
But does that mean the exhaust flaps are closing?
If so, I might need to understand how to do this mod to keep them open...