Crysis Warhead Tweak Guide
 

The writer of the original Crysis Tweak guide has updated his excellent article with info regarding Crysis Warhead.

If you are experiencing texture pop-in, you can disable texture streaming if you have a higher end system and get rid of the problem

r_TexturesStreaming [0,1,2] - This setting controls the streaming texture system in the game, and if set to 0, textures are not constantly streamed as you walk around, they are preloaded from a cache. While this increases memory usage, and hence may cause additional stuttering on systems with low RAM, for the most part disabling it should cause no problems and will reduce stuttering on most systems. More importantly, disabling it also appears to improve more distant textures without any real drop in performance.

there or tons of others excellent tweaks in this guide, so check it out!

http://www.tweakguides.com/Crysis_1.html