So looking up Left4Dead1 server commands I found these launch commands. They'll work on any Valve FPS!
-noforcemaccel (removes mouse acceleration)
-noforcemparms has something to do with desktop buttons
-noforcemspd is the exact same as CPL mouse fix it was originally intended for games like UT and quake that couldn't use the start up commands to remove it
Seriously this and disabling VSync have made Left4Dead1&2 into completely different games for me. I'm not sure if I'll use these commands come the LAN this weekend as it makes me feel like a complete and utter noob again.