Having problems with your check engine light? Want to run cat bypass pipes or a free flowing sports catalyst set up on your vehicle without having to reprogram the dme (ecu)? This adapter offsets the oxygen sensor about 1.5 inch from the gas stream. This achieves, in most cases, a sufficient measurement for the air/co ratio and increases the tolerance range between the pre and post cat oxygen sensors. In addition, the sensitivity of the oxygen sensor is also reduced allowing you to run a nearly any exhaust or catalytic set up, including bypass pipes, without the need to reprogram your ecu! Use only for the 2nd oxygen sensor (after catalytic)!