The flange between section 1 and section 2 won't line up and need the be rotate.
Also, the section 1 on E46 M3 is 3" shorter than the Z4M section 1. When I had my Z4M Coupe, I removed the OEM cats section 1 and installed an E46 M3 Supersprint straight pipe section 1 and needed to modified it.
Hope it help
