Glad to see those items found and deleted.
I can offer you some help links and suggestion for YouTube
Changing Buffer Settings with YouTube Center
Visit YouTube. To access your new settings, navigate to the YouTube homepage. ...
Open YouTube Center settings. ...
Click Player on the left menu. ...
Make YouTube videos load without pausing. ...
Stop automatic buffering or playing.
YouTube No Buffer (Stop Autoplaying)
https://addons.mozilla.org/en-US/fir...ube-no-buffer/
https://support.google.com/youtube/answer/74662?hl=en
Disabling hardware acceleration in the Flash settings
To disable hardware acceleration in Flash Player:
Go to this Adobe Flash Player Help page.
Right-click on the Flash Player logo on that page.
Click on Settings in the context menu. ...
Click on the icon at the bottom-left of the Adobe Flash Player Settings window to open the Display panel.
Try the above and see if anything helps