Missing sensors
I have a 2000 BBC 3500 4 dr.Chev.Truck thats missing the 2 sensors aft of the last muffler.I did take the VIN to chev & the drawing they provided me shows them to be there.Mine have plugs in them..I cant find any trace of a wiring harness--It gets 10 to 11 miles per gal at 55-with or without trailer??Thats what started me looking for the sensor problem..it gets the same milage with.without a trailer-Im to understand the front & rear sensors telle the computer wheather its rich or lean--Without them it retards the timing & increases the fuel?Any help provided will be greatly appreciated--