Hello, just got back from testing the right most sensor again.
I put the red probe in one of the sensor's holes and touched the black probe to the block near cylinder 1. Took a reading then moved the red probe to the other hole.

Prong 1: 1.680 kOhms
Prong 2: 1.665 kOhms

Car has not been started today so far. Current temperature in Arlington, TX is 75F.

So the values are very similar which is good. It would have been obvious the sensor was bad if one of the values was very different.

Oxygen sensor is less than 5K old, but if the car was running so rich then perhaps it has been fouled?

__________________
2006 BMW M5 "Heidi" @ 109,000 miles
2005 MBZ C55 AMG "Lorelai" @ 165,000 miles
1991 MBZ 300E "Benzachino II" @ 165,000 miles
1990 MBZ 500SL "Shoshanna" @ 118,000 miles

(On the hunt for a good used M103 engine as of 6/10/23, PM me if you have one to sell!)