Beg to differ with you Bob:
The DISA valve + proper programming appear to be the key.
Chipping the N52 in Europe is common. It looks like all N52s built for outside the North Amercian market utilize the 3 stage intake. The exception of course, in the US are Si designated models, E90 330i, and SULEV equipped cars.
http://ms-chiptuning.de/bmw/1er.html