I would unblock it. Otherwise, expect driveability problems especially during warm up but even when warm. Tip ins will not be instant or smooth and overall responsiveness will suffer otherwise. Even if this device improved atomization at the accelerator pump discharge nozzle, there would still be fuel puddling as it impinges on cold surfaces of the intake manifold passages as it weaves its way to the cylinders.
Some block the crossover to minimize fuel boil off when the engine is off after operating in hot weather and to prevent hard hot starting due to fuel vapors boiling into the engine and flooding it. But for me, it isn't worth it to block the crossover for these reasons.
Today's cars pretty much make all these issues go away with precise, well atomized fuel injection (both port type and direct fuel injection) and vapor storage and purge systems. And the cleanest cars have port fuel injection where fuel is injected onto the hot intake valve before combustion during cold starts and then switches over to direct fuel injection into the combustion chamber once the engine is suitably warm whereby the less effective atomization of direct fuel injection would be acceptable because the combustion chamber is hot enough to ensure virtually complete atomization.
