9-11 fps without airport and AI traffic is definitely not a scenery problem, but a problem with your system.
One thing very wrong with your system configuration, is a reasonably strong video card (I presume it's a least 512MB, if not 1GB of VRAM ? ), with a 32 bit OS and only 4GB of RAM.
This issue has been discussed several times on the forum, this is the worse possible system configuration, because with a 32 bit OS, the TOTAL addressable memory space is 4GB which means, the VRAM on the video card is NOT added to the overall memory available, but is subtracted from it! So, for example, an XP system with 4GB of RAM will probably have about 2,5 GB of free RAM available, and this has to be SHARED between Windows itself, all backgrounds services and applications AND FSX. Considering that FSX often requires more than 2,5 GB just for ITSELF, and you'll realize how this could be a recipe for disaster.
Note that, it's also very misleading to compare other sceneries and saying "I have better fps with that one". No, you haven't. You have bad fps with both with one being slightly less bad, but since our sceneries are usually made in a way to depend MORE on the video card, the also suffers more with such penalizing configuration, with the upside that, with a correct configured system, they usually runs very well.
You can't fix this by simply adding more RAM either. It would be a total waste of money because, since with XP couldn't see past 4GB anyway, you wouldn't see any benefit.
The only sensible solution is to INCREASE your RAM at least to 6GB or better AND (more important) switch to Windows 7 x64. Under this configuration, your OS will see all the available RAM, FSX will have up to 4GB all for himself, and your video card memory will be added on top of that, instead of cutting into your system resources.