And this is why in cars helmholtz resonators are typically only used in intakes to kill resonant drones due to the particulars of their piping, and are used in power generator setups (which run at a fixed RPM).

 

Try it without the BOV and associated hoses installed and re-tune your supercharger inlet TB "crack". I bet your whine goes away, mine did.

Unless your BOV is a sequential and properly set up, it will be leaking under boost.

 

Worth a go! cheers BarbyCar.