that sounds reasonable to me... i think i may be entering the realm of needing to just take it down to my local VW guy, he's good, but not cheap. so i usually try to trouble shoot myself first without hacking the old girl to pieces too much. I'm still tempted to try and attach a piece of hose to the blow off valve and see if the noise changes indicating that is where its leaking.
what you are calling a BOV, is actually an overboost protector.. and they are the biggest waste of time ever.
if your intake is off an actual AAZ, and not a 1.6TD, it should not have the valve on the side of the intake manifold..
those valves never let you make more than about 10-15 psi boost..
and they do indeed sound like a leak or a buzz when they are opening early..