it's not really a 2nd air filter, it's an emergency air inlet that opens when there a change in the pressure caused by the filter being submerged into water. just a little insurance to prevent water being sucked into ur engine. While this might never happen, I think better safe than sorry. It allows u to bring ur intake closer to the front where it might be more susceptible to water. I think a magazine did a review where a guy had his car with AEM bypass valve put onto a clear plexi tubing intake. Revved the car up and then put the end of the clear tubing into a bucket of water. The water sucked half way up to the bypass valve after which the valve opened and air entered from that point.
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