The problem has to be with the fueling. The timing modifications are older and have worked fine for a while, however this is the first time that I've tried to have this level of control over fueling.
That gives me an idea. The first step is not to attempt fueling modifications. This should give some pops and bangs (tested working earlier). Then reintroduce the fueling code but only change the fueling a bit at a time.
I will post a few ROMs up within an hour with those different ideas.