dont belive in louder or better performance is exactly the same no diferences
I made a bunch of runs switching the K&N in and out, noticed no difference whatsoever. Infact, my best trap was with the stock air filter. My 12.13 at the drag strip was with a totally stock air filter as well. But let me know if you want to buy my near new K&N, still in the orig box. I only used it a few hours.
But in all fairness, its not really the fault of the K&N. There have been numerous dyno tests showing almost no difference between running a filter and no filter at all.
1987 Grand National
2011 Alpine 335d M-Sport 12.9 @ 108.3mph
2008 Black 335i Sedan. 11.81 @ 119.2mph,
2008 Monaco Blue JB3 2.0 335i Coupe. 11.33 @ 132.77 mph
60-130mph: 6.95 seconds.