You need to relocate your O2 sensors and EGT onto the midpipe you just got. There are countless threads on the topic.
http://www.zpost.com/forums/showthread.php?t=331906
If you follow everything correctly, you wont have CEL.
EDIT: Here is another source with all the parts you need. + the bungs I already sent you the link for earlier
http://www.billswebspace.com/BMWZ4MS...stallation.htm