Glad to hear you are still working on it! I hope the comm pcb tells you something.
BTW, have you looked at lamp outputs for daytona at all? I have a feeling it's similar to virtua racing how it works but I'm not that clear how you have done that. Is it writing it's value back to itself in the same memory space or is it offset one way or the other? These two games seem to have a lot in common and it's the only model 2 game I can't get lamp outputs for (aside from the test menu, they seem to work there?).