I searched for a long time to find mine. It was on top of the exhaust pipe in an almost impossible to reach location. The easiest way to locate it is to simply run your hand along the pipe in front of your cat.
Mine is a '96 LT1 so it has two cats and four sensors and is much different than yours. Nevertheless, if you follow the pipe you will find it. These cars were not made with maintenance in mind.
After looking under my car today, I noticed that I have 4 sensors. One in each header, one right before the cat, one right after the cat. Now my question is...which sensor can cause the car to run lean?
Is it one of the sensors in the headers, or is it the sensor right before the cat?