Replaced the O2 this afternoon, took about an hour. First thing I noticed was that my rough idle immediately smoothed out. Can't even tell the engine is running at idle in drive, which is how it should be
. I was having some real bad random shudders at idle, so bad the first few times It happened I thought I got lightly tapped from behind!
Now the voltage readings from the O2 sensor are in the proper range, just slightly below a stoich mixture. I don't think duty cycle needs adjustment. The PO had a re-manufactured Bosch fuel distributor installed at the dealer before I got the car
...which was hellishly expensive. So AFR is something I ain't going to touch, because it's been adjusted somewhat recently. Unless it fails emissions when I take it back. But it better not, or it's owner is not going to be very happy with it.