Hmmm, somehow i don't feel much difference neither in performance, neither in graphics when using the performance package...
Just to make sure: You download those two .rar files, unrar using Winrar, copy the data folder to your game folder - start the game and play?
No, you also have to set up some sort of archive invalidation, otherwise the game will just use the default textures in the BSA archives. Get FOMM, it has a utility that allows you to use archive invalidation. You also need to change a line in your ini file, if you haven't done so already. Look for the bInvalidateOlderFiles line in the Fallout.ini file, not the Prefs one, and set the value to 1.