Whistle while you,,,, drive?

Currently chasing the sudden appearance of an annoying whistle from my Edelbrock carb.
I had the insulating spacer between the carb and manifold and took the carb off to do some rejetting and out of nowhere I have a whistle at idle and just off idle to about 1,200 RPM's.

I thought, ok fine I have a leak at the base gasket although I didn't see any reason for it.
Everything looked good and looked like it was sealing well.
Fine, I pick up another 3/8 insulator and put it on with no change at all.
I had already checked all the intake bolts, base gasket, and plugged off all the vacuum ports including the power brake booster with ZERO change even in the pitch of the whistle.
It is definitely coming from inside the venturi area.

So with Edelbrock square bore carbs on an Edelbrock spreadbore intake it is recommended to use the adapter plate and gaskets (never needed it before, but ok) I pick up the adapter and gaskets along with a 2 inch stud kit because the stock studs were already barely long enough with the insulator.
Put that all together and ZERO change even in the pitch of the whistle.

Alrighty then, the next try is the airhorn gasket (mentioned by Edelbrock) because my current gasket had a small tear where the air cleaner stud passes through. (I usually just fit it back in place before I tighten the carb top screws and it's never been an issue)
I couldn't see how that little tear around the stud was going to cause a whistle, but hey what the hell.:D
Nope, zero change.

Then only thing left is a possible partial obstruction in the idle air and transition ports as mentioned by Edelbrock in their support pages as a possible cause.

We'll see.:D

I posted this mostly for the information of what has been suggested as a cause and what of those suggestions hasn't worked.
I'll get it eventually because I have tons of patience with this kind of thing, but to have this suddenly appear for no apparent reason is a bit annoying.
Next is blow out the idle and transition ports and see if it goes away or changes at all.

The engine runs great just as it always has, but whistles at and just off idle.