A simple ECU reflash will get you up to the European Spec 325i performance range.
323i CA 2007+ 2.5 L I6 200 bhp (149 kW; 203 PS) 180 lb·ft (244 N·m)
325i EUR 2005–2007 2.5 L I6 218 PS (160 kW; 215 bhp) 250 N·m (184 lb·ft)
I spoke with a tuning company, and they said that on the Euro 325i they were able to produce figures around 233hp and 206 lb/ft.
Having this in mind, in 2008 I had exchange of emails with Upsolute, probably the same company we are talking about.
They refused to do anything for me locally thorugh their reps. I was hoping for a simple ECU reflash on my car Possibly if I was to send them my ECU it would have been a different story.
Here is their final answer received on January 2009.
I have asked our main programmer in Austria to reply if he thinks it's
possible I doubt it because checksum algorithms between the two ECU will
be completely different. We do not disable emission's controls due to
legalities, and putting the euro software directly on would be illegal,
we can though look at the differences between the key maps and match it
on your car without environmental system changes inherent in Europe. We
will keep you apprised, Regards, Rene
Your idea of removing the primary is tempting, but Quebec is coming with more regulations and periodic tests so there is definitely a risk. The 323i has ULEV2 cats, the 325i Euro has something different according to realoem.