Quote Originally Posted by Owl View Post
AEM Electronics suggests 18 inches from the head for placement of the O2 sensor. I was wondering if you should use one, or both exhaust steams combined. Assuming you have a good engine I guess it doesn't matter.
With a newer wide band placement is not as critical. Its heated and even when I have sample tubes stuck into the tail pipe it works short term. They are the manufacture so its best to locate it like they said as it may help keep the sensor clean. One or two is your choice. I have experimented with both and its usually close the same readings. If you only have one sensor and two pipes and are really picky, you could install the sensor in the second pipe as a check after tuning is done on the first. If its a 2 into 1 system you can put the bung at the y with good results. USA made o2 bungs are on ebay very reasonable so grab a few and head to you favorite welder. Be sure to grab a plug or two for when you are done.