I installed an aFe Pro Dry air filter over the weekend, and I feel like I actually hear the turbo LESS now. I know with most filters, it's either the same as stock or louder. With the stock filter, I used to hear a high pitch but fairly quiet whistle. When I first got my car, I actually mistook it for a distant siren. Now I hear no whistle. Is this fairly normal, or may there be an issue? Thanks!

 

I noticed a little more noise when I installed the AFE dry filter, not a lot just a slight increase. But I had a dirty stock filter that was quiet possibly due to being dirty. Was your stock filter still brand new?

 

No, it had almost 15,000 miles on it.