Have you done any work in the driver side panel by the e-brake? I somehow loosened the harness connector there and would get intermittent fuel pump not running, if I slammed the door it would then work.
As JM0413 says, jumps between Rich/Lean and O2 reading jumps from low value (~0.2) to high value (~4.8).
What you're describing is what I saw in the post I linked on page 2.
January 2021 update now available, see first post. Next month the list will contain selling locations and possibly other info.
34 new additions this month for a total of 1200.