once again i dont know about the game, but if those fake players has xp, then im sure you can add it to urself too.
Get a packet editor and record the fake players and examine the packets. find the packet that gives the xp and try editing your own xp packet.
at least thats what i would try.
WPE pro should do the trick, but it can't send packets back into games (usually it doesnt work on games) so you can only capture packets with it.