Patch: One of the easiest ways of improving map speeds be it for SP or MP is extensive use of the CAULK texture and adding area portals.
If I remember correctly where ever the engine sees the CAULK texture it wil not render it in game. AS for the Area_Portals, adding them as a thin brush in doors will close that room of from the engine until a player enters it, thus not drawing it until the player enters the room.
I think I've got that right, no doubt my esteem collegues from the EF board will put me right if I'm wrong.
Llawnroc