I was going to let this thread pass, but I have had so much fun installing my first and second air pumps, that I couldn't resist. First, the usual caveats: This is only my opinion being stated, I'm not a pro, and this is how I understand the system.
The air pump helps warm the cats up quickly by pumping more O2 into them than they would otherwise see from the enriched mixture burned through a cold engine. This is especially helpful for places like CA and Deutchland where the emissions laws are the tightest. I've been told that Germany has a 60 second after cold start emission requirement, which requires extreme design measures such as the air pump.
The pulley bearing is an odd metric size which is not available in the US. The bearing on the oe pump is made in Germany and the manufacturer actually has an agreement with DCAG to not export it to the US. This is because the US EPA requires auto manufacturers to sell emissions equipment at the component level only, not the component parts. This is to protect our blessed environment from people who would foolishly attemot to repair their $700 list pump instead of disconnect it and run without it. (Actually the pump will eat the belt if the pulley bearing seizes and the carbon pump vanes eventually seize.)
I actually contacted this vendor in Germany and started working on a plan to ship the part to a contact in Canada before I realized it was a fool's errand to do this much work on a pump with 150 k miles on it. The pump's average about 100 - 150 k miles. Another option woul be to mill the clutch pulley to accept a different sized bearing, but realize that any modified core will not be accepted by a rebuilder. The rebuilders all reverse engineer the clutch pulley bearing I'm talking about. It's a much cheaper unit cost to reverse engineer on a lot of 500 bearings than to do one at a time.
It is my understanding (wink,wink) that you can install a new pump and leave it disconnected electrically without any adverse effects. Most states perform emission tests on thoroughly warmed up cars, making the pumps a moot point.
you all have to make your own choices.