Difference between Injectors

[HMLyder]

Im look trough the part list on my terrano II and i see that the No1 injector has a different part number than the other 3 injectors.
Does anyone know what the difference are and why are they different?
On the old model, all the injectors are the same.

 

[makeitfit]

T2 has a sensor on No1 injector

 

[clivvy]

what he said.

 

[HMLyder]

My injector is leaking (wet around the injector)
So i was thinking of just changing the seal ring, but does this injector mailfunction often?