The 1GR-FE 4.0L V6 engine has front catalytic converters built into the exhaust manifold assembly. This performance header system replaces that entire assembly including the catalytic converter. This allows for free flowing, long primary tubes that enhance performance.
When the front catalytic converters are removed, the ECU will diagnose a fault setting a check engine light. URD has a little black box we call a rear dual channel O2 sim that is available to keep the check engine light off and prevent the catalytic converter inefficiency code from being set. Just click the box below to include the sim with your long tube header order if you need one.
Note: The stock crush to seal gaskets used in the connections between the Y pipe and the exhaust manifolds should not be reused. These gaskets should be replaced. You can select the "ADD GASKETS" box below to have two heavy duty additional crush to seal gaskets included in your order. Doug Thorley recommends that the stock cylinder head gaskets should be reused and new cylinder head gaskets are not included. The Doug Thorley Long Tube Headers and the URD Rear O2 Sim are not CARB legal and are for off road/racing use only.
The Doug Thorley Long Tube Headers and the URD Rear O2 Sim are not CARB legal and are for off road/racing use only.
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