You can pull that restrictor out of the airbox with your bare hands.
So I get around to pulling the air box out today but I can not find any "restrictor" to pull out , I did however notice that the air tube that goes to the air cleaner snorkel from the exhaust manifold is missing.
Not fully understanding the whole purpose of the air box, at this point I am wondering : If restricted air flow is a concern / suspect for bad MPG, Why not just remove the air box and turn the air cleaner cover upside down ?