This O2 cel fix actually has a miniature catalytic converter built inside and will help get rid of that annoying check engine light you get after modifying your exhaust or removing your catalytic converter, and sometimes even when installing a high flow catalytic converter.
This O2 cel fix with miniature cat will trick your ECU into thinking the stock catalytic converter is still installed. When you remove your catalytic converter, your post O2 sensor will see higher temperatures and greater flow of unburnt fuel.
As a result this will throw check engine lights (Cel, SES, DTC) typically the error codes will be P0420 (Catalyst System Efficiency Below Threshold Bank 1) and/or P0430 P0420 - Catalyst System Efficiency Below Threshold Bank 2).
For OFF ROAD use only.