No, no, no, no, no, no, no! That's just how the intake sounds. When you get to that RPM, the engine is sucking more and more air through the intake. For instance, form your lips like you're about to drink from a straw, and inhale slowly. Obviously you can hear your breath. Now do the same thing inhaling with a greater amount of force. TADA!!! Similar sucking noise!
That's how intakes are. You don't hear it with the stock intake because it was designed with all the baffles and the big box to reduce engine noise.
I personally LOVE that sucking/hissing noise!!! Don't worry about it. That noise just means that the intake is doing its job.
that sound is beautiful. the intake gets so loud that it rumbles something in my car, and i love it! i remember when i first installed my intake (or filter, all i have is a cone filter in place of the flat stock filter) it made this blow-off sorta sound everytime i let go of the throttle at higher rpms.