The fuel rail can hit 30,000psi. It's not just a LOT of pressure, it's friggin' phenomenal. If you remove a component, re-using it after the metal has already been deformed once during its connection could make it a failure point.
The Nissan service manual is quite explicit - Nissan tell their own service people to never re-use fuel rail/injector components. It's not really Nissan BS - it might be designed to help them make a few more $ off the sale of the components, but it also guarantees that upon the reassembly, it's not going to leak (if done correctly).
The self-learning relates to the ECU learning your driving habits and adjusting fuel maps based on that. The harder you drive, the more the ECU tends to pump fuel in.
The Nissan service manual is quite explicit - Nissan tell their own service people to never re-use fuel rail/injector components. It's not really Nissan BS - it might be designed to help them make a few more $ off the sale of the components, but it also guarantees that upon the reassembly, it's not going to leak (if done correctly).
The self-learning relates to the ECU learning your driving habits and adjusting fuel maps based on that. The harder you drive, the more the ECU tends to pump fuel in.