Make sure you are using a USB 2.0 with your controllers. We have just been discussing this issue in another thread in the forum.
With respect to the EGKK scenery, make sure you uninstall the original scenery first, do not drop another updated copy over the top of the original otherwise you will end up with some duplicated files. This will definitely cause a slow down!
I posted a link to an article about why you should use USB 2.00 hubs, alas no one has looked at it. I had this problem and changing the USB port from 3.0 to 2.0 worked wonders! If you only have USB 3.0 ports you may have to buy a USB 2.0 hub!
https://goflightinc.com/information/usb-3-0-solving-connectivity-issues-with-flight-sim-devices/
Turn off USB power saving on all your devices.
Charles.