They do work well and are a great option.
However often people install them and then don't maintain them properly. They need to be serviced at least once a year...
Is it really that hard to remove them, wash and re oil?
There were some concerns that the oil from the filter was contaminating the Air Flow sensors in some cars.
But K&N have done a lot of testing to try and find out if this was actually happening.
Their results showed that no oil from a "properly" loaded filter could be drawn off with the normal air flow through a system.
Maybe people are being careless and applying to much oil or not washing the filter before re loading it.
Either way if you maintain your filter as recommended by K&N it should be fine.
I have an S&B filter on my VW Golf for over 3 years and I've had no issues with it.
I even did this to my SC... I know it's ugly but I was experimenting to see if I could get a few more HP from my old girl.
It's not on the car now. It did change the character of the engine. It may have added a few ponies but I never dynoed the car before or after.
But it did make the revs drop very quickly which was unacceptable.
