I gather that the upstream O2 sensor is the one right in the center of this picture. I also gather that the catalytic converter (the "cat") is the bulbous part of the exhaust right behind this sensor.
Question 1: Does the cat consist of just this one part or does it include the second 'bulb' in the exhaust that appears in this second picture?
Question 2: This third picture shows the section closest to the tail pipe. I can't spot the downstream O2 sensor. Can you suggest where I should be looking?