This weld-in bung allows an O2 sensor to be screwed into your exhaust system. It's required for custom exhaust systems, and is also useful for air/fuel ratio measurements when dyno testing. A threaded plug is included to cap off when not in use. 

• Locate bung as close to engine a possible, without exceeding the maximum operating temperature for the O2 sensor. The suggested location is just down-stream of the merge-collector on each bank of cylinders.
• Sensors located after upstream exhaust system leaks or too close to exhaust outlets are susceptible to poor readings or influence of ambient air
• O2 Sensors exposed to exhaust gasses with too high amount of un-burnt fuel can lead to misleading readings. A possible lean reading.
• Locate sensor/bung 90° to exhaust gas stream.
• Locate sensor/bung in tube with a minimum of 10° up angel to prevent liquid build up in sensor element.
• Use stainless steel welding wire or rod when installing bung.
• Do not have bung plug or a oxygen sensor installed when welding bung in place.
• Welding can distort the bung so it is recommended you chase/tap the threads of the bung after welding.
• When installing O2 sensor or plug, use an O2 sensor compatible high temperature resistant grease on the threads.
• Use tightening torque suggested by O2 senor manufacturer.

*picture may not depict actual item