2015 cayenne v8 exhaust sound

[Fokker]

I’ve a pre Adblu v8 diesel. I thought it should sound better being a pre Adblu EU5. It’s the facelift model but is still muted. When in Park, it’s fruity but move to Drive and the exhaust instantly gets quieter and loses the rumble, is the system active?

Wouod be good to know if I can do no anything to keep the flaps open if so?

I’ve read that the pre Adblu cars should sound more fruity and I did drive a 2014 facelift car years ago that was a demo from Porsche which was much louder so I’m figuring my car could be louder as standard.

Any help appreciated.