Bax1 sorry to dig this thread up but did you ever resolve the problem with your MPU? I was working on a Tag Team last night with the same issue. Game would boot up OK. in test mode I could scroll through the audits but then it would hang on Lamp Test (lamp 2).
I was able to add credits but could not start a game.
BTW installed Freeplay ROMS from https://www.flipprojets.fr/Proms80B_EN.php using Piggydeux from acebathound
Cheers!