Looking at the numbers..
Probably cam n heads are mismatched.
Lemme see what heads you have on post 1....brb
Oh boy... what are .200-.500 numbers on those w2's and the header is too much imo.
Narrow power band r kinda indicative of more exh than intake charge. But I'm no expert and dont own a dyno. That intake manifold without any work only flows 'on my bench' around 245cfm.