Why would low lift head flow hurt power?

Hysteric said

So is using a smaller primary throttle bore and venturii size a reasonable compromise to make to overcome a lack of vacuum generation due to a the aforementioned issues?

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Depends on the build/situation etc.. Most people don't have dollars to do it the way you seem you want them to do it, Most are happy with larger less efficient engines with off the shelf parts, it cost time and money to build custom highly tuned engines like Nascar-Pro stock etc...
If that's your thing cool.