*sir dvldoc, do you happen to have any info regarding K&N Pro Series oil filters (PS)? I was only able to find:

K&N Performance Gold Series (HP)
100% at 40 microns
100% at 35 microns
100% at 30 microns
99.4% at 25 microns
98.9% at 20 microns
97.1% at 15 microns
92.3% at 10 microns
82.5% at 5 microns

I wonder if the the K&N Pro Series (PS) are having the same efficiency rates. Externally, I see the K&N Performance Gold Series (HP)series having a hex head bolt... but the Performance Gold Series (HP) seems to have more than 2x the price compared to the Pro Series (PS) of the same size...

Thanks!