I think all injectors, even in batch-mode pulse once per camshaft revolution. In TBI, it might be per crank revolution (no camshaft sensor). That makes the electronic controls simpler. Sequential just means that each injector's opening start is timed to its intake valve. The reason that sequential doesn't help at higher loads (and rpm) is that the fuel flow is high so the injector is spraying for sometimes most of the crank cycle, yet the intake valve is open for only ~25% of the time. Thus, the injector is spraying at a usually-closed intake valve under load. Sequential really only helps at idle, to reduce emissions and only slightly at that. As far as the details of the air flow and combustion, that still can't be well simulated. But, no need since they have engine tests stands and just play with the injector timing until they find the optimum settings.
