I always like to read reviews on air intakes by company's and all the bad mouthing that takes place and how they don't work.
First off I have had K&N filters on 4 different cars with no motor issues caused by the filter.
When you install any type of air intake they tell you to disconnect the battery. Once you have completed the install reconnect the battery.
Now your vehicle will not respond right away from installing a air intake. Yes it may sound cool. But the computer in your car can take up to a week to recalibrate all the fuel trims and throttle body positions. So when these company's do these wonderful test they are not letting the computer get used to the new set up. This is why the see minimal gains.
As far as dirt I always check my intake tube and throttle body and they are very clean vs what the filter looks like. So no additional dirt is passing the filter. And if you don't like to oil a filter go buy a AEM dry flow filter. AEM is also owned by K&N. And if you are really worried about dirt then get the addition pre filter screen.