NO NO NO!I have not mixed them not at this point when the problem started. They only thing that may have changed is that steam may have updated its version of the game but I left the standard X-plane 11 installation alone. in fact when I opened it to test it out it wanted an update from 11.25 to 11.3 which I denied and I still got horrible FPS Also so you know the X-plane 11 installer will dected and update the x-plane 11 steam version and after it is done it will still work if it doesn't just verify local files to go back to standard steam version. the only thing that is different between the to are the .exe files.