It's not clear how you upgraded. I think the only safe way to update the sim is:
- Uninstalling the previous version
- Downloading the FULL installer
- Installing the new version
This will not require to reinstall any of your addons, except those that change files in the simulator own folder ( this is a bad practice in P3D4, since it's longer required with it). When the simulator is installed properly, there's no reason why KMEM would perform any differently than with 4.3
