Firefox slow: FIXED!
For my system, I went to Settings and scrolled all the way to the bottom to Network Settings and clicked Settings. This opened a Connection Settings window and the first section is titled Configure Proxy Access to the Internet. My installation of FF had four proxy options to choose from and mine was set to Use System Proxy Setting. I decided to check "Auto-detect proxy settings for this network" and I clicked OK at the bottom and closed the Settings tab. FF took off like a rocket! After months of using Chrome because of the extreme slowness FF had, I can now continue on with FF and zip around the internet at warp speed. I am very happy!!