is the noise coming from the port? if so try smoothing over some edges in your port walls. round them over.
is it coming from around the woofers? if so find some foam material not some caulk that will stick to your sub and look like shit and place it under the mounting rim. Next time cut your holes a little better too.
if its port noise and you cant get it to go away by smoothing you are probably not going to be able to do anything about it. Is it almost a chuffing sound?
As for my feelings on exo. I wont say anything. There is someone who is a memebr here who will get all butt hurt about his little buddy.