Assuming it is just the wiring and the principle of minimum amount of errors. Most sense would be one pair is shorted. Means that actually another injector also squirts too much. This would get two cylinders overly rich, up to the point of non firing at all.
Second option: a little bit less sensible. One injector is shorted, another one is completely cut off. But than you would have seen one of the lights not flashing at all and most probably a violently shaking engine.
But at least your getting to the solution! Now solve it and don't swap the 1.6l in
