Karl nailed it about the 323 exhaust. If you decide to go the route he stated, I have a 328 catback in great shape for $50 if you want it. And also a straight pipe midsection.
"Cassie"///Mpowered 93 318is 5speed (S/C'd 95 m3 swap)
2007 X5 3.0si (Wifes)
2001 330i DD