Trying to understand Manifold choices

I purchased a 69 swinger 340.
I hope that this doesn’t sound too stupid to you but I am trying to drive myself crazy sometimes when I should leave everything as it is…..

I am trying to read as much information about the 340 so I have a better understanding on what works and what doesn’t work.

I have read over and over again that the stock manifold was or is a very good manifold and the only downside to it is the weight it has.

The next best option was the LD3(spelling?) and the RPM Air Gap, both flowed just as good or just bit better, and definitely much lighter.

So I am trying to understand why would someone install a plain Performer intake over the stock intake, it has to be only because of the weight and or cost. I don’t believe that it flows as well as the original intake!

Nick