Its completely normal, the stock air intake is designed to reduce the whistle noise while slightly affecting performance.

When we switch to the cold air intakes we get added performance but gotta deal witht the whistle.

I kinda like it....

 

My favorite thing about the CAI is the faint "Blow off valve sound" everytime you get off the throttle. Makes me think my truck has some power under the hood. lol

 

I used to have that "blow off sound" but it went away when I got the superchips and started messing around with the shifting. I went back to stock earlier this week to see if it made any difference in my vibration and the blow off sound was back. Reinstalled the tune and it went away.....

 

You need this.

http://www.youtube.com/watch?v=Q-NKvDSL7sM