Indigais (Aivis) is breaking a 328 here: http://www.bmwhaus.ie/forum/showthread.php?tid=3016&pid=37038#pid37038 you'd have to spend an awful lot of money to get a better exhaust than a full 328 system for a 323, a few of us have it fitted to e36 323s and are delighted with the results especially with an M50 manifold. Although I fancy something like an Eisenmann or Scorpion cat-back just for the noise. Good luck anyway.