My car came with ram air and a K&N air filter. I had never had a K&N before so I really didn't know anythin about maintianing them. My friend had been telling me that I needed to clean it for about 2 months now. But I never did because you can't drive you car for like and hour when your cleaning it and I never knew when I was not gonna have to drive. So I did it yesterday. Went and got the $10 (US) cleaning thing that had the spray cleaner and the oil. It was really really dirty. I followed the directions and knocked the loose dirt out and brushed it. And the liberally sprayed the cleaner on and let soak in for 10mins. Then washed it inside to outside Still dirty. So I procceded to spry cleaner on it until it was running down the filter and let dry for about 20 mins. Washed it again waited for it to dry. Still dirty but better. Sprayed half the bottle on it, almost killed my self with those fumes. Don't spray inside. Washed, Let dry for an hour, still dirty but some white showing. So I said screw it don't have time any more. Oiled it and put it back. It's not completely clean but much better and I can tell a huge difference already. The car had been sounding kinda bad and had a flat spot in acceleration between 4 and 4.5ish k rpms. Now it's gone and sounds a lot better too. So I know for most people this is common sense. But if you've not done it within a couple months I would reccomend doing it. Made a huge difference for me.