I had air ball issues with my monger out of the box. To fix, I removed the plastic top and slightly bend the metal brackets holding that plastic piece on so that the plastic was level with the playfield once reinstalled.

Another issue I had out of the box was that the monger wouldn't register all legitimate hits.

One problem was that the blue bumper brackets at the base of the monger were a bit too wide and a hit to the side of the monger would cause the metal bracket to hit the main monger plate and keep the monger from moving back far enough to register a hit. I just slightly bent the brackets in so that hits to the side always register.

The next thing I did was to add a washer on each of the three posts that attach the monger to the main plate to pull the monger slightly closer to the optos.

Both of the above tweaks made my monger register shots flawlessly.

Oh yeah, I forgot all about those. I also tweaked the height in this manner after leveling the flap brackets.

I used the flipper fidelity kit. AMAZING sound! Get it! Also get some glass rattle tape along with the speaker kit, you will need it.

1.6 is the latest code version.

The glass rattle tape is for the edges of the playfield glass. The whole cabinet will vibrate enough after adding the speakers combined with the shaker that it will rattle and make a terrible noise.

The board in your picture should only have one set of optos connected (for war machine). The other connector pair is unused since there isn't another opto used in the game. I assume Stern doesn't have a single opto board and just uses the dual opto board on everything.