It is really a bit early to say in regards to N55 compared to N54. I will say that at moderate "Stage 1" levels of mods (basically just a tune), at this early stage they seem very similar. I can also say that at high RPM, the factory system simply won't run more than about 14-15psi no matter how we drive the control system. Perhaps when the decat pipes come out we will get more boost out of it, but early indications are that the N54 will probably have the edge at higher mod levels simply due to more flow capacity in the turbos. However I think this will only make a difference to small % of people running lots of mods. Most customers do either tune only, or just basic add ons like decat pipes, intake and exhaust. The big mods after that are meth, FMIC, but these mods are more visible and tend not to be used by most BMW customers.