not evil,just hungry
the easiest way is to do a ceiling warp. continue to the room after the gate (dont fall down to the scan post). Jump on the door then jump towards the empty space on the other side of the door. The next room should load. You can now ceiling warp into whatever room the map is not on. to do this simply morph on the ceiling, press into a slant with the joystick (not always necessary), and hit unmorph. You should drop into the room. Move close to the door to reset the map to the correct room (otherwise you will crash when another room loads) and continue on your way.
http://www.youtube.com/watch?v=hY4kjuihX70&feature=player_detailpage#t=143s
http://www.youtube.com/watch?v=hY4kjuihX70&feature=player_detailpage#t=143s