It would be nice to see actual flow data using a standardized method conducted at several different differential pressures, say .5 to 2.0 "hg.

Venturi size is not necessarly the defining element for air flow. There are several aspects that will effect the flow. Slight changes in shape and contours can have a large impact on air flow.

Another item of note is that on my 4781, the boosters are different than on my 950. They are thicker and look like they would be more restrictive to flow.

With all that, it is hard to believe that the 950 (1.375" venturi) flows more air than the 4781. However, on my car, the 950 is 1 mph faster, and .2 sec quicker.