40k miles is very low for a cat to fail without another issue causing it. Easy way to check and see if you AOS is pumping oil into your intake. Take off the tube I have circled in red, it comes directly from the AOS, check it for oil.
If there is just a slight bit of oil that might be normal, not sure on that though, but if there is a decent amount of oil I would look into replacing the AOS before it mucks up your cats.
EDIT: Handle that hose gently, even though it was originally made flexible, mine was very brittle and broke when I was moving it out of the way during my intake upgrade.