I'm curious about this as well. I posted in the F12 Forum the question of what the N55HP has that's different from the N55 that gives it that little extra boost in power.
What I'm really curious about is how much REAL power it has over the N55, as the N55 is very underrated (at 280 RWHP putting it around 330-340 actual crank HP).
'13 F10 BMW 535i Sport
: Jet Black/Black-Anthracite : Premium & Technology Packs/Sport Auto Trans/Camera/Park Distance Control/Heated Seats/Tinted Windows/Blacked Out Markers/Performance Spoiler.
Ordered: 2015 Porsche Macan S / SportDesign
Ex MB's: 11/10/06 E350 "Sport", 02 S500 w/ Every Option.