I have 2 HKS air pods (running the standard GTR BOV, which won't make much noise), they make a "Sucking" noise when the turbos are spooling and a "Choo" noise after releasing the throttle.
No matter what, your APexi air pod will flutter on stock or running higher boost.
To eliminate the 'Flutter', box up your air pod, get a custom air box made up or you can buy one to shield your pod off.
JJR Cold Airbox Assembly - Nissan Skyline ECR33
- http://justjap.com/store/product.php?produ...=272&page=2
Many ppl on here do it, BUT it will not eliminate it completely as you still have the pod on, but it might just lessen the 'Flutter' sound.
To eliminate it completely, reinstall the standard air box.