I'd recommend installing at least a 3-wire O2 sensor considering the install distance from the exhaust port. The sensor needs to be hot in order to send valid info. The 3rd or 4th wires bring the sensor up to operating temp.
BTW, when manufacturers install two O2 sensors (before and after the converter), the second sensor is merely a feedback to the ECM letting them know all is well with the primary sensor.
Sherwood Lee
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