These settings will help you increase everything in game..
/com_maxfps 250
Unlocks your FPS in COD4, Gains FPS, less Lag.
/cg_drawfps 1
Shows your FPS in COD4, upper left corner (or use FRAPS)
/cg_drawlagometer 1
Shows a meter, to display if your lagging or the server is.
/cg_fov 80
Increases your Field Of View, slight advantage. Better looking screen.
/cg_brass 0
Disables the shine of the guns, a FPS booster.. less visual
/r_multigpu 1
COD4 doesn't really benefit SLi, so change to 1 or 0. See if it works for you.
/r_drawdecals 0
Disables GFX effects (dirt, snow, paper etc etc) less visual..FPS booster
/cl_maxpackets 100
Ping Booster
/cl_packetdup 2
Ping Booster
/rate 25000
Another Ping booster
/snaps 30
Don't have the background info for this one, but does improve ping