False Air .....FOUND!
 

I would get a code for bank2 sensor 1 enrichening after installing new cats. I replaced an old O2 sensor but would still get the code after driving a couple of miles. Crawled under car and found a small pin hole leak behind the cat. That's right, BEHIND the cat at the weld. This is well downstream of the O2 sensor in front of the cat. Welded up the hole and no more problems. Evidently, the corsa cross over tube is so efficient at scavenging exhaust pulses that it pulled in just enough air from behind the cat through that little pin hole to trigger sensor to add more fuel. Unbelievable. :thumbs:

Good spy work on your part!

Details are the difference between something puzzling someone and actually finding the problem.

:seeya