To be honest the vibration is not bad at all. I feel people who complain about it are a bit on the picky side but it's your car and you are entitled to that view point.
I defiantly noticed some vibs but nothing crazy. It's obvious why the void was there in the first place to increase driving comfort and lesson vibrations. When you start modifying the car these are some of the to be expected items to anticipate. Especially if you are putting a hunk of rubber in an area by design is not supposed to have anything there.
I like the vibs, because race car!!
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Airaid CAI | Borla S-Type Catback | Amsoil 10w30 and MTG Trans. Fluid
382hp 387ft/lb | 1/4: 12.9 @ 112mph