You have found the correct screw. If you remove the plug the adjustment screw is inside the hole.

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Mercedes Benz Master Tech - Retired

So, Mr. RPM. the top screw is the "plug" with allen screw underneath? (I love to confirm things)!!

That is correct. Just be sure to reinstall the plug or you will have a vacuum leak.

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Mercedes Benz Master Tech - Retired

Many thanks, RPM.

That's what makes this forum like 'gold'. You can't even get this info from a dealer tech, who - more often than not - doesn't know which end is up (or down).

There are several dealer techs on the forum who are very helpful and know these cars. I myself worked for two different dealers for a total of 16 years before going the independent route in 2000. Anyway Im glad I was able to help. Have a good day. Robert.

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Mercedes Benz Master Tech - Retired

RPM:

I don't know about what you earlier advised.

Just removed screw, and tried to insert the 3mm allen wrench. All it did was contact the threads for the other screw, but didn't turn anything. Then I inserted a thin allen wrench. Went all the way down hole, and contact throttle plate, making it go up and down.

What gives?