Yeah, still have my SC E38 but sold the Euro 635 and bought a 928 S4. Been busy enjoying life off grid with my Land Cruiser.

The noise is the slower decelerating whining noise that come after the engine deceleration noise. I removed the air filter housing and can't pin point it but its probaly not from the engine but definitely under #3-4 intake manifold.

Don't know if the dealer tech forgot to plug in the DISA valve after PCV recall service which may cause air to reverberate on deceleration.

The pcv heater valve, DISA, MAF is the only thing in that area so not sure what else it could be. Thanks.