If all the injectors were tested and working then is the injector harness plugged in the whole way? Is the MPEM sending a signal to fire that injector? While the engine is not running, disconnect the injector plug off the injector and plug a volt meter to it. Start the engine and see if it registers any voltage. That tells if the pulse is at least getting to the injector. No voltage then check the wiring or see if you can plug volt meter into harness that leads to wire of injector back where it is generated at the MPEM. Check the wire from MPEM to injector and make sure of no pinched wire, broken or cracked insulation. If you can find both ends of the wire then ohm it out to see if it is conducting and not shorted to ground.
