OK, let's first uninstall xserver-xgl, I don't think you want that (I don't have it and I don't run laggy). Other people have complained in other threads about lag on all different types of cards and I'm tempted to say its because of xserver-xgl, so you're gonna test that out for me It can always be reinstalled of course. Please post the output of all of these commands exactly as they appear in your terminal.
Originally Posted by knight666
sudo apt-get remove --purge xserver-xgl