Ram air is not as easy as it sounds, and yes, for the fuel to flow correctly all the areas have to be pressure equalised.

When I first fitted ram air to the NSR back in the Victorian era we had all sorts of issues. Lots of carb setting, even as far as different float heights, drilling holes in slides etc.

I had two years of messing with ram air on the NSR looking for the best set-up. Then a further couple of years messing with RS125 & 250 ram air in Japan.

You can't just seal up the stock airbox and expect it to work. Engines are complicated and fickle little buggers and they don't like being set up wrong.