Dave is right about the cross over restrictors.
It does aid in fuel atomization, it prevents fuel from puddling at the bottom of the intake when the motor is cold.
For performance though I would block them cross overs off. Most of the performance intakes and or heads don't even have cross overs. Depending on your intake and or heads you may not even have cross overs. If it don't have the ports then you don't need the block off plates or restrictors.