Date registered: Feb 2008
Vehicle: 2004 W220 (S430) ; 2001 R129 (SL500) Sport
Location: Alabama Gulf Coast--formerly Charlottesville, VA
Mentioned: 0 Post(s)
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I don't know, but I'm guessing right around the place where the air filter housing connects to the throttle intake on the engine.
There is an R129 forum on this site--scroll down from the main forum page or go to the bottom left of this page and use the "forum jump" convention. Your car is an R129 chassis, and there is a room full of people on that page that will have the answer for you.
"Don't pick a fight with an old man. If he is too old to fight, he'll just kill you."--John Steinbeck