[Mohuska]

I agree above with the post about using a normal O2 sensor vs a wideband O2 sensor. Normal wideband O2 sensors are not linear in their response and are very sensitive to temperature changes.

First, for any O2 sensor to read accurately, it must be mounted in the collector, downstream from where your headers join together. Don't every place an O2 sensor in one cylinder, if you are going to get anywhere near accurate readings.

Second, many O2 sensors do not have a heater element in them. A heater element is necessary to ensure that the unit is always within the tolerable bandwidth of temperature for the sensor to respond. Too cold or too hot and it will not be accurate.

Third, There can be no air leaks in your header system. This will draw air upstream from the sensor and show an abnormal lean reading.

Fourth, quite often, a sensor can show lean when it is actually running rich. If you are smelling unburned fuel, and your O2 sensor is showing lean, lean out the mixture until you are showing stoicmetric readings. For normally aspirated engines, the stoicmetric AFR is 14.64:1 for gasoline.

If you really want to get accurate readings, mount a wideband O2 sensor in the collector....either side is OK...or there are systems where you can mount one in each side and use a toggle to flip back & forth. One of the best units I have seen is the FJO Racing unit....there are many options...but this is a pretty good one....

One more thing....when choosing O2 sensors, try to use Bosch ... It is the most linear of the available O2 sensors.

Mike