the best way is to ask the $tealer for part numbers OR go to
www.bavauto.com, to find the right part for your specific car model.
I have a '97 Active and I just replaced both o2 sensors, bought from bavauto.
and everything plugged right in.
One thing, everyone recommended the tool, but I could not use it, instead I used the monkey wrench an it worked great for leverage, both to losen and tighten the sensor.
The only thing you have to do is to be careful not to slip.
just my .02 cents!
Cheers !!!!!