W116

1978 450 SEL High Idle 2000 RPM

I have just acquired a 1978 450 SEL and based on the records the motor has about 35k miles on it since a complete rebuild. It starts up and runs fine (wants to die if you give it gas when cold) once warm. It drives great but the idle is high at about 2000 RPM cold and 1700-1800 warm. Not sure where to start.

Vacuum? Is there an idle control of some sort that could be bad?

I don't see an idle adjustment and don't know these gas engines so I'm lost.

Thanks for any help!

-Mark

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