The info there is a bit vague and not really helped by your post.
Am I right in thinking the 330i engine has the variable length manifold but the 325i doesn't but they are the same block etc so all you need to do is put the 330i manifold on and reflash the ECU with the 330i map?
If so then yes I would think you would just have to get someone to stick the 330i map on your cars ECU.
edit: the intake manifold looks like plastic so I doubt there is much you can do to fettle it. BMWs are pretty good anyway and their standard non-turbo maps are also pretty good which is why they probably don't even bother tweaking it and just quote the 330i figures.