Nobody ever reported a problem before. However, KLAX is surely more heavy on textures memory usage than KJFK, which was designed with the 2008 PCs in mind.
It's not very easy to understand the issue, with no details about your system. And, even if you have a good system, if you use a very demanding addon airplane, which is eating away all your texture memory on the video card, the video driver, in order to save your system from crashing, will start to swap in/out VRAM and normal RAM, which result in a very large performance loss, especially under DirectX 9.
Try to:
- Switch to DirectX 10 and see if there's an improvement.
- Try different resolutions in the Addon Manager (like 2048x2048 instead of 4096x4096).