It's actually confusing as hell:
- The N54T diagram vacuum tank drawing orientations confuse the situation, along with the fact that the Z4 uses more current software for their designs, which shows a literally different visualization (i.e. coloring).
- The E89 drawing connects the vacuum tank and solenoids in matching location pairs, whereas the N54T diagram shows the back vacuum tank mounting to the front drawn solenoid. I only point out this fact as it could cross up representation.
- The Z4 uses two different p/n vacuum canisters. The N54T uses two of the same canisters (which happen to match one of the two part numbers used in the Z4). This is probably a packaging/mounting difference, not a functional difference.
- To your point on the solenoid connections ... the N54T diagram only shows a vacuum canister connection. They don't show the connection to the turbo side (to the little elbow), whereas the Z4 drawing shows both the canister and "elbow" connection.
My vote is the drawing could well be wrong. It wouldn't be the first time. I just had to rebuild the fuel rail on an M44 ... diagrams for fuel delivery are so wrong its not even funny (hard line versus soft line, o-rings missing,etc). But I'm pretty sure those solenoids have a vacuum side (they are not interchangeable connections). One other side-note: pretty cool how two solenoid from wastegate vacuum and they both "T" into a shared line. Not sure what the dirty details are there, but correct me if I'm wrong: one could continue to get vacuum to both wastegates if one solenoid shit the bed?
Filippo