I have that sticker on the truck I bought. How do I know if it's just a sticker or if it has one? What's the purpose of a filtercharger?

 

I believe, what K&N calls the filter charger, is the oil used to coat the filter media after the filter is cleaned. You may have a K&N filter, easy to determine, your filter media should be purple/black with an oily coating.

 

it is a waste of money that is known to let dust particles into the engine.