Ignition timing for stock cam/heads Magnum 5.9?

So I'm right at ~15* initial timing and it's significantly better! Still not impressive but better.

I did discover that the vacuum line (connected to the side/lower part of the carb) is totally inactive. So I guess I'm running on only mechanical advance.

Could this explain why my car feels slower than it should or is the vacuum advance really only helpful in establishing initial timing?