Airaid TBS question

Last night I put the covers back over my cut outs and could then hear a very noticable hissing/air sucking/whistling sound. I assume it's from the TBS cuz it did not make any such noise before I put it on with the cut outs shut. My question being is it not sealing properly and lettin air in under the throttle body, or is that how it is supposed to sound??? I could only ever hear the hiss before when i put my foot in the accel but it has done that ever since i did my intake. truck still running fine with no codes but i was just curious. It sounds pretty cool but i just hope thats how its supposed to be.