low O2s running lean stumble issues help please!

the grey smoke could be something as simple as your egr seeing vaccum at idle ,a bad connection or faulty vss or low voltage seen by the pcm are your likely sources (Two of these are at your pcm connector ) . the 84 im working on does this intermittantly . It sends a signal to open vaccum to egr valve in turn blowing hot exhaust gases back into your intake when it should not . If you cant get a properly reading o2 signal to the pcm the car will never adjust its fueling correctly like it should , imo