Help plz

Hey i also have an purple/black screen and i fixed it with the mat_viewportscale 1 command.
But i currently run a autoexec.cfg(found no mistakes in the cfg.)to have better fps.but after i typed that command the textures were much higher and also the character models were and i had 30-100 fps(with my autoexec before the update i had 80-120 and more).Now i found out from another thread http://teamfortress.tv/forum/thread/1863/1 post12.
So my first question is if it helps to get the old autoexec settings back again.
If not how can i fix it?
If yes wheres the location of the materials.vtf folder?