I have exactly the same problem!! But unfortunately, I already have the Anisotropic filter set to 16x.
The only possible explanation, is the Anisotropic filter is not enabled. Maybe the video driver is not reading your settings, either because you haven't set it to override/enhance the application setting, or another tweak utility is interfering with it.
Blurred runways, assuming you run the scenery with the resolution it was designed, which is 4096x4096 for most of the textures of JFK V2 ground, are always caused by a lack of Anisotropic filtering, which is used precisely to fix the blurring that results from the low visual angle typically involved during an approach.