Thanks you,
Yes, stock airports can be somewhat heavy on fps, because they use lots of library objects that are optimized to be re-used worldwide and placed automatically, and this doesn't always work well, especially at very large airports, that might have hundreds of them placed, so different kind of optimizations can be done.
We are working right now on a free update which will feature the new runway 9C that opened this days, which will be available for P3D first, and for MSFS shortly thereafter.