Its either what it should do or you havent plugged a hole. Some have an extra hole or two that you have to plug because of different makes and models. Such as with my SR performance CAI needed a rubber stopper cause I didn't have a cable like newer models that it goes with have. But if it isn't a loud whistle or doesnt sound good at all its probably just needs a small little stopper.
1999 V6 Mustang Dark Satin Green , SR CAI, BBK 65mm Throttle Body, Screaming Demon Coil Pack, SR Lowering Springs, Pioneer Stereo, 2 12' inch subs and 1600watt amp, Green Calipers,