Cat/CEL Trick kit for MS6 engines running the ATP Racing Downpipe. Easy bolt-on kit installs inline with the rear 02 sensor on the 02 bung to prevent the CEL due cat delete. Off road use only. PLEASE NOTE AND ACCEPT BEFORE ORDERING: This device during the course of our testing has been found to only be 80% effective (on average) at its purpose. This is due to the simplistic design of the "trickery" built into this component and add to that, the sporadic range in which the rear 02 sensor values are output back to the ECU. There are no electronics used on this assembly. While the majority of the vehicles tested went for months without ever exhibiting a CEL after installation, some test vehicles exhibited the CEL only after a few days. This device is not guaranteed to completely eliminate the CEL. In addition, please scan your ECU for codes before installing the device. If you CEL is already lit for other reasons to begin with, this trick DOES NOT correct those other problems triggered in the ECU that are unrelated to the catless downpipe.