Injector is dead. Long live the Injector.
But which one? I have no idea what I am doing here.

I have a 525d e60 2004 with M57d25tü engine. What I would like to know is are the injectors from 3.0 engine the same? Because technically it is the same engine. Also, are the 06 to 08 e60s injectors same as mine?

Also, apart from making sure I buy the right injector by looking that serial number on it what else should I watch out for?

I know it's recommended to change all the injectors at the time but that will have to wait a bit. Until then, I wanted to buy one, used or refurbished so I don't drive on 5 cyl and then later I'd buy brand new 6 of them so I know I am good.