Enlarging PRP doesn't always help

The heads I’m most familiar with, wrt SSR issues are BB 906 and 915 heads.

While I have seen very good flowing examples of those where the SSR hasn’t been lowered/laid back as much as I typically do(when heavily ported), I’ve never been able to duplicate those results.

On the other hand, I’ve had some ported examples show up here that had less that stellar flow, where I was able to pick up 20-30cfm by doing nothing but rework the SSR.
It’s pretty easy to end up with a big valve(where the whole intake runner has been ported) 906/915 intake port that’s stuck in the 240’s at .450-.500 lift, and either doesn’t show any gain beyond that, or the numbers go back down.