Secondary turbo shut off valve

[Discodicky]

Has anyone had an issue with their P/N LR043939 Compressor shut off valve, otherwise know as the Secondary Turbocharger Recirculation & Shut off valve?
On the 3.0 D4 Secondary Turbo.

My problem is that when accelerating briskly, as soon as I reach 2400 rpm when the 2nd turbo comes in I hear a one-off loud very short/quick/brief cracking noise identical to the noise a whip makes when cracking it.
It appears to be accompanied by a very brief hiss rather like when a wastegate on a "hot" Subaru WRX goes off.

I need to confirm which I'll do in next few days, but I think that by accelerating gradually I can 'drive through' the rev range and get over 2400 without the whip crack. Either that or the noise is not so prominent as opposed to accelerating briskly when overtaking a vehicle or changing down to go up a hill which quickly sends the rpm over 2400.

[Graeme]

The valve could be sticking causing it to not open progressively. The valve can be hand-operated after removing its cover behind the front right wheel or can be exercised by supplying vacuum to the tube where it attaches to the solenoid at the top of the front of the engine, noting that there are 2 solenoids in the vicinity.

[Discodicky]

FYI, I finally got to the bottom of the problem.

The exhaust pipe exiting the 2nd turbocharger has a crack around its flange.

Stainless steel so not worth risking a repair as no one will guarantee it.

Ordered a new pipe assembly, the Genuine was cheaper than aftermarket.
Not too bad a job to do considering.....

Approx $1300 ex LRA Melbourne.