Seconded on the AC Delco o2s on Rockauto. Cheaper than many aftermarket sensors.
I don't see any point in replacing the downstream o2s out of precaution. Their only purpose is catalyst monitoring. They don't affect performance or efficiency at all. They work till they don't,
I could see it maybe if you're replacing the exhaust, but if you don't have any codes I say leave them be.
The upstream o2s are different of course. They affect fuel trims.
I don't see any point in replacing the downstream o2s out of precaution. Their only purpose is catalyst monitoring. They don't affect performance or efficiency at all. They work till they don't,
I could see it maybe if you're replacing the exhaust, but if you don't have any codes I say leave them be.
The upstream o2s are different of course. They affect fuel trims.