only thing i can think of is an airleak

its conceiveable that you could have damged the AAV and this is now vibrating and causing a whisle, but if that would happen (highly unlikely) then i doubt you'd be able to hear it as itd be so quiet!

have you checked and re-checked all the vac hoses etc. around the inlet manifold area? are you confident that the main boost hose from Xover pipe to TB is seated 100% securely?

try spraying carb cleaner all round the inlet manifold at idle and see if the revs change at any point (dont use WD40... carb cleaner is combustable so the revs should rise if any manages to get into the engine )