Not that this is particularly germane since my experience is aeronautical. In my old Mooney... which sports a carbeurated 360 cu, 180 hp 6 cy air-cooled boxer engine, there is an "air filter by-pass system fitted. This re routes the intake air from a rather circuitous system that includes an air filter, to a direct - straight shot to the carb mouth from right behind the propeller, path. At about 150 mph this produces about 2" of manifold pressure difference for ram-induction. Nothing to write home about, and certainly resulting in questions about efficacy at 60 mph, since physics dictates a (v)squared=energy relationship.
The question of induction restriction is quite another subject, however. On an old RZ 350 and a dyno, we discovered that drilling 4, 1.5" diameter holes in the airbox lid increased the hp about 2 hp per hole...... the 5th hole added nothing more.