[BimmerBri]

This question may have been asked in the past, although I was unable to locate any specs.

So, my prior vehicle was a 07 Z4 3.0Si
This vehicle produced an extra 20-25 horse power over the standard 3 liter inline six N52 3.0.

I now own a pristine 2007 e92 w/sport package, although as you all know this motor puts 20-25 less HP than the Si in the Z4.

Seeing as there has been so much talk about performance upgrades to this motor, I thought I would ask if any one knows what BMW did to produce the extra HP in the N52 Si motor? Is this the manifold swap I hear people referring to on this forum or did they do something entirely different?
Any insight would be appreciated.
Thanks all.