When you did this conversion to your 320i, what did you tell the referee you did? Supposedly, you cannot tamper with the emissions equipment, even if you are upgrading to a newer style feedback system. I would think the only way (legally) a referee would let you do that is to do an engine transplant (for example, to put in an '82 L-jet 3.3 from a 733i with feedback and cat into a 530i).