I can't believe I read the whole thing! [See below.]
The bottom line:
In an actual test, a truck as shown in FIG. 1 was extensively operated with and
without protrusions, and gas mileage records were kept. The truck was operated
at various speeds under 55 miles per hour, on a predetermined course that
required both stop and go city driving conditions as well as expressway driving
conditions. After protrusions… were added, it was found that fuel consumption
was reduced by about 17.2%
Search as I might on the Inter-web, I can't find anyone making aftermarket
pieces that closely resemble this idea.