With the help of Marcus Trevino and Josh Tidmore I was able to find and document the scoring bug that has been discussed as being used in competition. I feel keeping this exploit secret doesn't serve the community. It's better for everybody to know rather than just a select few. So here it is:
In a nutshell, the exploit has to do with the second phase of Emerald City Multiball Jackpots. In order to use the exploit you do the following:
1. Start ECMB (Emerald City Multi Ball) by lighting all the character letters and locking 3 balls in the center/right ramp.
2. Complete the first phase of ECMB jackpot shots by hitting a character rollover and then shooting the right/center ramp. After all three characters are collected, you then shoot the throne room to approach the Wizard.
3. The second phase involves rolling over each character button (Tin Man, Scarecrow, Cowardly Lion) and then shooting the throne room to collect the jackpot/reward
You're supposed to hit each character + throne room to get a jackpot.
The Jackpot starts at 20k and then increases by 10k for each subsequent Jackpot, so ideally completing the second wave would yield:
20k + 30k + 40k = 90k total points for all three character jackpots in the second phase.
However, if you avoid hitting the second and third character rollovers, and instead keep shooting the throne room, you can rack up consecutive, cumulative jackpots in perpetuity (20k + 30k + 40k + 50k + 60k, etc.) theoretically scoring endless amounts of points and jackpots that keep increasing.