I've got a similar problem with 1993, 3500 crewcab. it has a wire hanging down near the sensor, one sensor wire is plugged in, but there's no place to plug the other one in. It also gets 10 to 11 mpg but at 70 mph, gets about 7 with 28ft halmark loaded. If i pull my flat bed trailer with car on it the truck doesn't even know it's back there and get over 10mpg. BUTTT!! when the truck is first started the check engine light is off and it runs really good, but after a few miles driven the check engine light comes, and there is a noticeable difference in the performance on the bottom end, but no change in gas milage. No one around here has a plug in for the computer so i don't know what code it is.
Zip.