Pulling V.A at idle
Those are junk gaskets. Don't know why people still use them, especially now since carburetors really need to be kept cooler to keep the ethanol in check.
Open the secondaries "a little" just like I described. Don't expose any of the t slots...that is UNLESS they are RIGHT THERE ready to be exposed if you crack them open any....and I'm sure they're not, so just "a little". Close the idle screw until the T slots are perfectly square, and don't mess with the idle screw again. Use the timing and air screws to get the idle right. You might even have to remove the carburetor again to give it a "little more" on the secondaries, but don't do it with the primaries.
I don't think this is gonna solve your vacuum advance issue though, because the primary t slots are pretty close. I'm thinkin it may have an incorrect gasket as someone eluded to earlier. But, since you have the carburetor OFF, there's no sense in not getting "all this" perfect.