[twag4]

Most of the time, longer intake runners (however they are employed either different manifold or spacers) will add to top end. It was a simple way back in carburetor days to get a good performance boost in the upper half of the RPM range. (Think stoplight to stoplight and drag racing) Carb spacers also did the same thing, but with less affect. Sometimes it actually robbed bottom end performance though. I have built a few Chevy and Ford small blocks back in the day, and this is some of what we did. For more bottom end you went low rise dual plane manifold.
Edit: BTW I did forget to mention that adjusting and sometimes rejetting the carburetor was a must. Curious how this is possible without a remap of fuel injection at the very least