Also yes, BMW went from a twin
Single-Scroll to a single
Twin-Scroll setup from N54 to N55 in '09.
Technically as far as the engine is concerned, nothing changed. The exhaust of the Inline 6 engine was still split into 2 channels, 3 Cylinders each, and fed to a separate Scrolls, instead of separate Turbos.
I suppose this could have been for simplicity, or weight saving, or space saving reasons?
This is a diagram of the N54:
You can see what I mean where the Cylinders are split. Important to note though, the diagram is not 100% accurate. They show Cylinder 1-3 going to one Turbo & Cylinder 4-6 going to the other. I don't believe this is actually correct, it was merely for the diagram's sake.
Cheers,
Emile