Thanks to Zelghadis, half the credit goes to him, through his 5 turn in zoltun exploit i was able to find an infinite method
Latest june 28th 2012 Zoltun infinite Loop XP reward.
VIDEO OF THE EXPLOIT
So what you have to do:
A - booster
B - Leecher
1. A creates a game on Act II Quest 8, part 3 (enter Zoltan Kulle Chamber)
2. B joins.
3. A kills ZK. B stays in the city.
4. After ZK is dead B leaves game clicks "Resume Game", run for Black Soulstone, TP back to city, Turn quest in, Join A's game.
5. A take Soulstone, B leaves game.
6. B leaves game and turns in
7. and after that B resumes his own game (A must have the quest to turn in) the trick is that u must have auto join off , A requests B "Request Party" and B click's accept there will be a significant delay in joining the A's game also an ERROR there was an error in matchmaking service B WILL NEED TO LEAVE 5-8 SECONDS AFTER ACCEPTING INVITE TO PARTY.
8. B will see that both of you are in same party in the menu.
9.A will have to leave party after 5-8 seconds (For this to work) and B resumes and turns in.
10.A Resumes and repeats step 7 & 8.
repeat step 6 & 7
this results into an infinite loop, it is a bit slow but still its infinite, no need to kill zol'tun again and again.
*UPDATE* In order for the method to work 100% effectively, i've learned that if you Delay the leave game with B (Leecher) for 6-8 seconds after accepting invite from Host (A) & you wont get the error of cannot join this game right now, which will result from the method to work 100% and avoid failures / waste of time.