Ok i installed a subwoofer in the back of my 240d and i had to drill a 3 inch hole in carpet through the metal into the trunk for it to sound right. before i drilled i checked to see if anything was gonna be in the way and there was one thing... a plastic bubble thing... its about 2 feet long and 1 and a half feet wide and it goes right into a spot on the roof of the trunk. there was a tube connected to it and when i cut it air hissed and then stoped... when the car is on the tube connected to the plastic bubbles sucks in air. what the heck is this thing and do i need it? can i just cap off the tube and call it a day or is it actually important