K&N Air Filters

You may get a few horses but 10-11 is not going to happen. If yu use a cone filter/induction kit then make sure the air supply to it is separated from the main heated engine air.

I had a K&N panel finter in my E39 and gave no extra power but the extra bit of noise was nice.

As the guys say above, you'll need cold air to gain any advantage from a filter.

Have seen cone filters put on the older diesels (tds) to great effect... the sound is fantastic - great whistle off the turbo. People actually turn around to see what is making the noise.

We were looking into putting one on 02 e39 530d - but would need an adapter pipe to go from a wierd oval shape (to fit that engine) to a suitable diameter circular pipe (to fit the filter)... no joy! Don't know if your's will have the same oval fitting or not - but be sure you can get the adapter pipe before you splash out and buy a good filter.

Let us know how you get on.

Denis

I've read too many stories about these filters not offering the same quality of
filtering as standard filters. I'd sooner have the inside of my engine clean
than a bit noisier!

I have reverted back to normal paper filters. I had a jetex filter that was really difficult to clean so it was never fully freeflowing. I now change the paper one every six months and can't detect any change in power.

The K&N I put in my car 2months ago has made a difference.Its without a doubt, brought my lower end power up a notch.  I dont notice any more horses at the high end of the revs, but as i said, it made a HUGE difference low down.  I would say get one, ive had no poblems, and also a BMW troubleshooter I know told me it would do no harm to the car.  There also is more of a grunty noise, and when she revs high it does draw attention, but when driving normal, its nice and discreet.  I got mine on ebay, wannt cheal, think i paid about �70 inc post.  best of luck min what ever you decide.