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I presume GM's Tuned Port Induction with it's longer runners and port injection showed good efficiency gains over it's predecessors. Probably the biggest improvement came from having dry runners vs wet such that there weren't any more rich or lean cylinders. Then the O2 sensor could really do it's job and optimize mixture strength for all cylinders. But everything has had these features for quite some time now.
I'd imagine the big fat plenum ahead of the runners mitigates pulsing at the MAF to some- small or large?- degree.
Beyond that I think the same notions we apply to exhausts also apply to intakes: runners small and long enough to promote flow momentum at the desired rpm.
Yah, I know that all helped a lot.
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