Package Tracer shows as an installed extension in the System Detail list next to the question.

You can uninstall an extension in the extension Manager.

• "3-bar" menu button or Tools > Add-ons > Extensions

• https://support.mozilla.org/kb/disable-or-remove-add-ons
• https://support.mozilla.org/kb/uninstalling-toolbars

Note that your System Detail list shows that you have a user.js file in the profile folder to initialize prefs each time Firefox starts. The user.js file will only be present if you or other software has created this file and normally won't be present.

You can check its content with a plain text editor (right-click: "Open with"; do not double-click). The user.js file is read each time Firefox is started and initializes preferences to the value specified in this file, so preferences set via user.js can only be changed temporarily for the current session.

You can delete the user.js file if you didn't create this file yourself.

• http://kb.mozillazine.org/Preferences_not_saved
• https://support.mozilla.org/kb/Preferences+are+not+saved

You can use this button to go to the current Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

Worked great, thanks