Upping the Party Members in Single Player and TCP/IP
Typing "/players X", where X is a number between the current number of players and the maximum (8), in the message box will set the effective number of players in the game (in single player, open Battle.net and TCP/IP games only). This will increase the Monster Difficulty, Experience, and Item Drops.

this is what i was talking about i couldnt find it the frist time i look on the summit tho.