It's the interior temperature sensor duct for the ACC. There's a small blower in there somewhere that draws cabin air in through there to the sensor that tells the ACC what the interior temperature is.

__________________
Craig Bethune

'97 SL500, 40th anniversary edition

'04 Olds Bravada (SWMBO's)
'06 Lexus ES330
'89 560SL (sold)


SL--Anything else is just a Mercedes.
(Kudos to whoever said it first)