the conversion guys and those who run "up front carbs" on model engines both have the same potential problem.
The airstream passing from front to rear over the carb can raise hell IN the inlet .
lengthening the inlet (adding the "venturi")will sometimes move the airflow problem.
angling the mouth of the "venturi" will sometimes help.
The air signal to the diaphragm is usually, also a culprit in these setups.

the carb's original design, which is to use the signal from the crankcase for fuel delivery, gets all fu--- up when the airstream on the inlet and the diaphrabm is a variable.
These "patches" are referred to as many things-but venturis- they are not.
The old term velocity stack is better -FWIW.
The car guys who have access to an on board computer tuning program can benifit from low restriction inlets -but as you mentioned - this is not a great idea all by it's self