Would replacing the stock air filter with a K&N air filter represent a real upgrade in performance? Just wondering... 2006 330i sedan Sapphire black Premium/sport packages
I don't think so either, I have a cheap cold air intake on my car that came with some generic cone filter on it, after driving for half a year with the original filter I swapped it for a K&N cone filter and didn't notice any difference in performance, not even on the butt dyno that said, they are a reputable company, and because the filter can be cleaned and re-oiled there's no need to replace it, so if you need a new filter for your car anyway you might as well get one
I recall a chart where Conforti compared K&N to a stock filter. The K&N did worse as it got dirtier allowing more particles into the intake. You can always do some reading. http://www.bobistheoilguy.com/airfilter/airtest1.htm Google K&N comparison
