2018 RS5 only one exhaust valve opens in dynamic

[jimw]

Hi guys. new to the forum!

Have a question about my 68 plate RS5.

2 months ago driving down the motorway in dynamic mode my friend who was in car behind me at time told me that exhaust gas was only coming out of the right hand exhaust

After stopping at the destination to check, I noticed that the left exhaust valve was closed and that indeed smoke was only coming out of the right hand one. This is with the vehicle in dynamic with the hand brake on.

When the engine is off, both exhaust valves are OPEN
When engine is switched on in comfort mode, both exhaust valves are CLOSED
When engine is switched on in dynamic mode on P or N, both exhaust valves OPEN
BUT as soon as I change into D or S in dynamic mode, left hand exhaust valve closes and only the one on right hand side is open, and exhaust gas only comes out of the right hand side valve

Is it normal for this to happen?

Thanks in advance