they suck, as long as it still powers up don't worry about it other then see if you can keep the moisture out of it, sometimes the valve on the tubing going to the exhaust fails allowing condensation to be blown into the air pump, othertimes it's a bad design on the duct feeding it, it's not a required part but it will throw a check engine code, you can make used ones from 850/960 volvos work by changing the cover on the big end and electrical connection on the small end, pretty much every obdII bimmer and volvo has one that can be made to work
all america wants is cold beer warm cat and a place to take a poop with a door on it