This is strange, my manifold has no separatio, it is one big opening, but smaller than the adaptor.So I can put the adaptor on top of the manifold and grind to equate sizes, no problem about thining down the wall of the manifold too much?

The opening in the stock manifold is fairly large. On my A12, I didn't enlarge it. You can see how big the stock opening is in this pic:

The adaptor that came w/ my 32/36 looks like the adaptor on the left,no separations, just a larger opening on one side, like that one, but when sitting it on the manifold,the manifold(trying to remember, I have not seen it since replacing the carbie ) ... was smaller, so part of the intake flow must hit this area.I think my manifold is smaller on one side, larger on the other, but the semicircles never touch each other, no connection, , I will double check.
Jaime