To add some info to the short acceleration video that was at the start of this thread.
Check out these three acceleration videos on Youtube:
528i (N20)
528i (N53 European 3l 6cyl) 258hp
535i
The 528i (N53) and 535i both take around 24,5sec from 0-200km/h.
The 528i N20 (4-cyl) takes around 32,8sec from 0-200km/h.
Around 8sec more than the 6cyl 528i, even though it's just as quick to 100km/h... As you can see the N20 528i starts to struggle (compared to the 6-cyl cars) at higher speeds and looses at lot of time from around 150km/h and upwards.