So I have a Weapon R intake.. I love it, but I get this "hotrod" sound at idle... Not loud, but noticeable if my radio is off and it's all quiet in the car. Is this normal, or do I need to check something to eliminate this sound. It sounds like my car needs maintenance when I am at idle.. HELP!!!!!!!!!!! Also, does anyone know what diamter I need for a new filter. Thinking about adding the K&N filter if it's possible?? Please adise.

Thanks,
Rock