Bought my car with 32,000kms on the clock in 2007.
It now has 137,000kms on the clock.
I drove it from the dealership and that weekend fited an Inbox K&N filter.
I clean it every 10,000kms and use the spray that goes with it to re lubricate it, and I have never had any issues.
Before when I owned my Honda V-tec, I bought that with 150,000kms on the clock, and drove it up to 256,000kms, and had to K&N Cone filter on that, and no issues there as well.
My wife has the Honda 180i, we got it 4 years ago, and been running the K&N inbox filter there as well, no issues.
It comes down to maintanace, and keeping it cleaned and lubricated...but it can work.
Don't expect power gains, and on a bmw there isn't really a noticible difference in the sound, like on a CitiGolf, for me its more about the fact that in 8 years I haven't spent a Rand on airfilter, just washing it, and keepig it clean, and if you take what an airfilter costs at bmw, I am sure I saved some money.
PS: That is my choise and my oppinion, and I not saying anyone here is wrong in sticking with OEM filters. :thumb: