My fuzzy memory is that the OEM throttle body rating on a Magnum 5.9 was 600 cfm at 1.5 inches of Hg drop.

Several people sold ported and “blade blended” Magnum throttle bodies but power gains were minimal.

My 1995 Magnum 5.9 V8 MAP sensor would read 1.6 inches Hg at wide open throttle at 4000 rpm.

One of the crazier things I did was check the accuracy of my MAP sensor by driving up Mt Mitchel in NC, stopping several times to compare MAP to barometer.

I discovered that the 2 EGR outlets just below the butterflies caked up with carbon deposits that must have reduced flow.

Do not forget that pre-Magnum there was an OEM TBI fuel injection throttle body.