IM replying to you. because your not running its highest textures that you need at 3gb video ram to run, its normal textures need something like 1.2 - 1.5gb of vram
Its stupid but its ID
[Edited by SIL3NT-DE4TH, 10/15/2011 6:26:30 PM]
The game engine is supposed to auto-detect the best settings for your hardware, but it often uses the lower quality 4k textures when your card can run the better 8k ones. I had to create a config file with lots of options including one which forces it to use 8k textures instead of the 4k and it makes a big difference.
The texture 'popping' happens because the game doesn't auto-create a cache folder that it needs to temporarily save the textures for the areas you look at in-game. After creating that folder and adding it's directory to the config file (or the Steam game launch options) it fixed the issue.
All the info you need about the best graphics options and how to set up a config file can be found in a sticky post in the Rage section of the Steam forum.