I pulled these injectors and noticed some engraved numbers on them. PO told me they were 550cc so the 550 engravings make sense to me but there is also another number engraved on the metal below it on each one.

These are Bosch 028015026 and seem to be OE for some VW/Audi applications. I tested resistance on each one and they measured 12.1-12.2 ohms.

Anyone have an idea what the numbers mean?

 

Just a serial number. If you find out who serviced them, you should be able to track down flow numbers and such. I know I did this with some very old ID1000s, before I knew they were ID1000s.