Hi Big Bil,
Air leaks anywhere on the intake can mess up your fuel ratios etc. Have you changed the Air Filter? Does your car have 2 o2 sensors- all have one at front,sometimes another behind the cat box? Also check all the rubber hoses at the back of the engine-ones to the idle valve etc-they can have hard to see leaks, or flattened. If the o2(front) sensor is u/s, the fuel system should be running in open loop (fault mode)-comp should tell you this-if sensor ok, might be high resistence on wiring- grotty connection, hope some of this helps.