A few days ago a bought a complete k&n intake kit for my 06 Titan. Before I had my factory airbox cut out at bottom to almost look like it was shielded from motor as much as possible. It was very loud when I stepped on it. I could hear it over my flowmaster 40 series exhaust. Put the k&n kit on shield, tube, and breather lines. Its much quietter. I would have never guessed! I think its the 57 series since it has the black polypropolene tube and emissions tag on shield. Any thoughts?