AIR FILTER
 

...can anyone help me decide which is the best/performance wise air filter for my 2002 4.4l X5?

How much money are you willing to blow?

....lets say 40$-50$

Stick with OE BMW. If you want to spend $600 go with Dinan.

..ok. anything special about K&N Air Filters?

I have heard a few complaints about the oil that K & N filters use causing damage to the air flow sensor and such.

...so better stay with OE BMW than this a?..

I would. I don't think you would get any substantial or noticeable power gains from using a K&N in the stock box. If you want more power go with a CAI.

The INDEPENDANT tests show that even a dirty OEM paper filter flows more CFM than the engine requires.

They also show an increase in the particulate matter from the K/N CAI type setups.

Yep, even more reasons to stay with OEM.