That's the first and probably last time I'll ever hear that! There have been thouands of Dyno Pulls that show an increase in BHp when switching TO a K&N, and this one guy all by himself is right in saying they work worse than a regular filter? Not likely!
Oh! Oh! This just in, Synthetic Oil robs Horsepower from your engine - Conventional Oil makes more power! One test proves it...
The biggest complaints I've seen on cotton gauze filters (K&N style) are in extremely dirty applications, such as off-roading and rally sport. The quantity of dirt is more than the filter can handle, so the filter clogs easily. In street use, the cotton gauze receives magnificent marks from most all after-market retailers, including Bavarian Auto, Turner Motorsport and Active Autowerkes. Turner and M3 websites carry the Conforti with the foam filters. I've never heard anything bad about these filters either.
Bottom line, the rumors about cotton gauze filters ruining engines are just that, rumors. Experience and testing by professionals proves otherwise, regardless of what ONE person might have experienced.
And yes, over oiling the cotton gauze, especially in a computer-controlled BMW with a mass airflow sensor, will result in oil being pulled into the airline, covering the sensor and throwing off your A/F ratio.
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