You guys are right of course -- the turbo in the N55 is not a sequential design, nor an active variable geometry design. I should always double check myself whenever I use the word "impeller" because I use it inappropriately to refer to the turbine fan. My point is simply that the turbine fans in the N55 are designed for low threshold, reduced lag, and high power. I don't understand the nuances of how the blades are designed differently to take advantage of the separated manifold.
Pretty good summary here:
http://kilometermagazine.com/artman2...Turbo_Six.html
But I want to see a better cutaway than what BMW provided in the Press package.
Any advantages to a manifold/header divided 6 ways, with separate inputs from each cylinder to the turbo? Complicated mess.