I don't wanna go on about this for days but this explains the TwinPower vs Twin-Turbo confusion, using the N55 and N54 as an example:
BMW’s TwinPower Turbo Technology is substantially different from the outgoing N54′s twin-turbo powered setup. With Twin-Turbo, two small turbochargers are used to increase the engine’s output, both spooling up at the same time as RPMs grow. With BMW’s new TwinPower technology, the N55 actually features only a single turbocharger instead of two working in concert.
The single turbocharger of TwinPower design is what is known as a twin-scroll turbocharger. It is an attempt to combine the advantages of using two small turbochargers and the singular housing design of a single turbocharger setup. With the twin-scroll design of the N55, BMW claims an advantage in both torque and the RPMs at which maximal performance arrives combined with an increase in fuel efficiency.
N13 1.6 L single turbocharger petrol engine with TwinPower Turbo, Valvetronic, and High Precision Injection
BMWs TwinPower (single turbo - twinscroll)
Sorry for the jack SN1P3R