K&N sucks big time IMO. I only use paper elements, mostly because when I got this turbo it had big time abrasive damage to the wheel, that may or may not be K&N's problem but I was worried it might be since I had heard similar things from some of the Cummins guys.
I've heard that before. My truck has the early style Banks kit on it, so it was probably put on when it was fairly new. The PO didn't do very good maintenance and repairs, and what he did do shows evidence of being pretty shoddy work. Judging by how rusted the turbo inlet side bolts are, I would say it is very unlikely that my turbo has had any repairs or any replacement parts (like a compressor wheel). It looks like it has never even been apart. If it has, it was a L-O-O-O-N-G time ago...
All that being said, it still builds 2-3 PSI tooling along at 2000 RPMs/60mph, and will build boost up to around 9 PSI when I really get on it pulling a load or going up a long hill. In other words, it still works just exactly as it should.
Seems to me that if the K&N filter was letting stuff through that would damage the turbo compressor wheel it wouldn't work that well and build boost like that...
One thing I have to agree with Mel on though, that big rectangular box does get in the way when trying to wok on just about anything on top of the motor!