O2 Sensor on 1985 2.3-16v

[BenzMacX]

I have been getting extremely poor gas milage, about 270-285 miles to a full tank (about 15.8 MPG, assuming i am actually using 18 gallons of the 18.5 gallon tank as i drive on reserve for a little bit). I know i have a gas leak because i can smell it, but i can probably find that on my own, but if you have had any experiences with gas leaks on a 16v feel free to share. I noticed while working on the car that my O2 sensor is not plugged into anything. The sensor is in the exhaust system, but the wire goes no where. I looked on my brother's 16v and our sensors are in completely different places, his is right before the cat, while mine is located on one of the pipes before they merge into one pipe (4 pipes go to 2 pipes go to the main exhaust pipe). Is this where it should be? and if it is, what does the wire connect to?

Thanks,
Jim