68 340 Exhaust Manifolds vs TTi Shorty headers

Do you think that the tests shown above indicate exactly what the question asks.
Do headers increase power by improving exhaust flow.
Folks used to scoff, say headers only work over xxxxx rpm.
In fact, the test show better results at near idle.
I suggested years ago that headers would even improve town driving fuel mileage, and test results indicate you'd use less gas pedal going shopping.

The 1 st test is fine as shown

But, again going to the air pump logic. . .

If you keep the restrictive puny exhaust system, designed for a specific exhaust flow, even making cast-iron manifolds with runners for direction, bigger passages etc, all to easy exhaust flow, . . . Why ?

Keep the 2 1/2" exhaust system, - (pump outlet), - - - then add a 4 barrel, a high-rise manifold, bigger camshaft, bigger heads/valves, bore, pistons.

Essentially open up the "air-pump" opening to 6 inches . . . AND ignore the puny, untuned, unscavenged exhaust, that every race engine in the world designs with great attention to the "few" horsepower improvement goes against all logic.
Ever looked at/studied F-1/Indy car exhaust systems .

I look for performance by the ounce, - everywhere.

Good luck