They're talking about the water seperater/inlet silencer that's just behind the little grill on the air inlet. You really get no horsepower gains. That little hole at the bottom of the plate is
not where the air goes in, that's to let water drain out. Air travels up over that plate.
If you want to take it out, the easiest way is a hammer.. you might feel some gains on the ass-o-meter, but that's purely psychological... no actual horsepower increase unless you go the whole nine yards and make a ram air system. just my 2 cents