The Bonalume Lambda adaptors allow you to delete the primary catalyst and not get a check engine light. They are to be installed on the post cat O2 Sensor.
2011 E90 M3 ZCP - Individual Moonstone/Individual Amarone Extended/Individual Piano Black With Inlay:LINK!!!
1994 Euro E36 M3 Sedan - Daytona Violet/Mulberry:LINK!!!