I don't know exactly what is done to the N52 to pump out more horse power in stock form but I would guess it is mostly tuning. I did a little searching and found this...
http://en.wikipedia.org/wiki/BMW_N52#N52B30
Quote:
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The N52B30 is available in three versions, all displacing 3.0 L (2996 cc/182 in³). However, each version produces variable maximum output depending upon the application. With a common engine displacement, the output changes result from the omission of the variable resonance system, dual plenum intake runner system, and the variable back pressure muffler: 190 kW (255 hp) at 6600 and 300 N·m (221 ft·lbf) at 2500-4000 rpm is the first and most produced version, while the second one is more powerful at 195 kW (265 hp) at 6600 and 315 N·m (232 ft·lbf) at 2750-4250 rpm.
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Make sure to look under the title:
Applications in the US Market (taken from BMWUSA website 07/10/07):
not the Euro version.
Here is some aftermarket help:
http://www.e90post.com/forums/showthread.php?t=45158
I would suggest checking out e90post for more info on the N52 since it comes in the 2006 325i & 330i and the 2007-2010 328i, which all have different power outputs that I believe is because of tuning.
Good Luck
