I live in New England and it keeps the snow from packing into the engine compartment when I'm driving in the winter. In the summer it forms a vacuum thathelps the air pass through the radiator and by the motor. It also lessens the high pressure that you get at the firewall and keeps some of the road grime off the motor.

Other than that there is little reason to have it except to make it hard to change the oil and **** off the Jiffy lube guys. Butif your the type of person to let Jiffy lube or any other like place work on your Audi you don't give a rats butt about the things mentioned earlier and you can just leave it off or sell it to someone that lost theirs.

 

I think it also has something to do with lowering engine noise in the cabin. ...Read something about it stopping the noise bouncing off the ground and back onto the floor while the car is moving... might be totally off the mark here...

I keep mine on as the winter salts and crap here in NE willeat through everything and keeping some of that crap off the motor sounds good in my book...I even made an aluminium "version" for my GLX .

Cheers
Massboykie