Headers vs 340 manifolds

My 73 Duster (post 129) benefited to some extent just from getting rid of the torsion bar pinch, as well as the tiny pipes coming off the manifolds. But neither my 65 nor 67 Barracudas had that pinch or the small pipes - just full 2.25 pipes off the manifolds. Of course, the latter two also benefitted not only from headers, but also from increasing the pipe size from 2.25 compression bent to 2.5 mandrel bent. But I'm convinced the headers were the main gain.