Well, the only way I can see on this carb for the PV to get vacuum is from the opening in the base plate that was covered. And if the power valve is open, that fuel would be coming out of the booster, correct ? What I know for sure is that the idle changed a bunch with the other gasket, and the manifold vacuum also stabilized. Before it would stay above 10 in. then drop to about 5 in. and the motor would almost die, then it would cycle back and forth. now it's rock solid at 9 in. plugs are dry now too. I'm not a carb expert, but changing the gasket made a big difference, that's for sure.