This post is for informational use. If you plan to install a header here are some things I have ran across and may help when getting all the parts together before your install. I have the OBX Maximizer (1 7/8" runners and 2.5" collector) header installed on my 2012 sedan. Originally I had the upstream air fuel ratio sensor installed about 3" away from the head on only #4 cylinder and the downstream was in the collector. After about 100 miles the CEL came on with P0420 cat code and the engine is running VERY rich. After doing research and talking to my techs that work for me the upstream needs to read all 4 cylinders. I started looking for o2 extenders and could not find one for our cars. I found out that our upstream sensors are a 5 wire wide band air fuel ratio sensor and the wires CANNOT be extended doe to too much resistance. After looking around and being on the phone with my vendors I have found that there is a sensor that will work. It is used on the 2007 Porsche Boxter with the 2.7l. Bosch part #17276, Denso part #234-5108, Walker part #250-25015. These sensors are 850mm (about 33.4") and will reach down to the collector with ease. Now for the downstream sensor. It CAN be extended because it is only used to read the cat efficiency. You will need to use a spacer that comes out in a 90 degree for space and to trick the computer. the rear o2 sensor needs to be at least 2.5" or more behind the upstream sensor. I hope this helps.
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January 2012 Ride Of The Month