My sons '88 300TE recent purhase... attemping to fix stalling and odd misfire...

Ok, so I buy a Sears multimeter with duty cycle....
Figure out how to connect it.... Black pin to pin 3 on the connector..
Its reading steady 85% with ignition on.. and engine off.. so California car...
Starts car... reading varies 78 to 90 ish, so assume 85% ....
Figure I can adjust it down a bit... to 70%ish....
Put in the allen wrench...push down... turn it a bit... one way..... no difference.....
Turn it a bit more.... and a bit more..... maybe half to one turn.
Engine stalls.
Now it wont start!
Cant remember which way I turned it!
Turn it back... I think about one turn...
Still wont start!
:Thumps head... shuts hood and goes indoors:
Ideas?

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2009 Mercedes ML320 Bluetec