Woodentop said:
I would suggest that the OP contacts a BMW dealer. One of the 320 series is not rated to tow although I cannot remember which one. The fact that it has a towbar fitted means nothing.
This is good advice as I pointed out data bases can be wrong. However if you have the car, then a quick look at the weight plate and see if it lists the GTW as being bigger than the GVW. THe difference between the two is the guaranteed towing limit, though some manufacturers did list a higher max towed load, provide the car was not fully loaded. I don't know if BMW ever used this method.