+1 for the K N, use one on my bike too.
You may be interested to read this report here. The author installs a K N filter on his BMW 1150. This too is unscientific, but Webbikeworld does seem to have good and well written articles.
Be sure to scroll down to "UPDATE: Case Study - July 2009"
There you will find the author (he has 40yrs experience as a mechanic) had a deeper look inside an engine with 187,000 miles that used a K&N filter. "K&N filter was installed by his son about 100,000 miles prior to my repairs & he's not sure when the last time it was "cleaned". " Read on for details....
http://www.webbikeworld.com/t2/k-n-air-filter/
Quote taken from article :
Stats:
1999 M-Benz E-320 with 187,000 miles and no oil consumption complaints.
V-6, M-112 ,3.2 liter motor with aluminum heads & block & automatic transmission.
Closed loop, HFM fuel management system using a Mass Airflow Sensor ( MAS)
K&N filter was installed by his son about 100,000 miles prior to my repairs & he's not sure when the last time it was "cleaned".
With the heads and intake off I thought I would take a look at the dirt and oil residue levels throughout the intake system, starting at the air filter. I also looked at the cylinder walls for any signs of scoring.
Note: Our MAS are VERY sensitive to ANY contamination whether liquid or solids! We are frequently replacing MAS for fuel adaptation values that have turned on the "Check Engine" light.
The adaptation values on this car were perfect!
My Findings:
I found NO traces of oil or dirt of any kind anywhere in the intake system or on the MAS. Everything was clean and dry.
I found NO scratching or scoring on the cylinder walls.
Conclusion: This was not a scientific test, just what I observed while the engine was apart.
It does though,
throw some doubt, in my mind, of the claims made by some that using a K&N air filter can cause damage to a MAS or the motor itself.
.