Originally Posted by shahramghs
N55 had more potential because the twin turbo can compress more air.However, Stock its not as good as N55.
Actually that's not true stock vs. stock. The N55 makes peak torque at a lower rpm and it feels a bit torquier off the line. But it also runs out of steam up top moreso than the N54. The N54 engine actually makes about 20hp more up top than the N55 engine, so for straight line acceleration/WOT, the N54 is the faster motor. Numerous dyno tests have backed this up.