Injectors are controlled by the ECU. Many times, the injectors being installed are at least double the size of the stock injector. Without telling the ECU then injectors being controlled have a different flow rate, the ECU will not be able to properly control the pulsing of the injectors. Many times, the engine will not be able to start with the stock tune driving higher flowing injectors. Your tuner may be able to send a temporary base tune that will allow you to drive the car to them for a proper tune.