You'll need an OEM european section 1 BMW PN 18307836633 for the cleanest install. Stock USA 02 sensors can be used by moving their routing from the passenger to driver side of the engine bay to reach the rearmost 02 location. There is no splicing required, a few zip ties etc. I completed this install with CSL headers in 2019, zero CEL or issues since. 10K miles and a number of track days
Thread with installation videos here
https://www.zpost.com/forums/showthr...=331906&page=3