After fixing various other issues with my E320 - I have one last minor niggle.

When applying light throttle, around 1100 rpm - the revs will surge up and down about 400 rpm. This only happens when hot. Say about 85 C engine temp.

Also when hot, coasting down hill sees a small pulse of about 200 rpm also around the same RPM.

Every other aspect about running the car is perfect. No Codes.

Other things replaced include:

CPS and K40 - to fix a hot stalling issue and a non restart till cold.
MAF - Rough running and surging at idle issues.
Wiring harness is perfect - have cut back and inspected wires.
Head Gasket done - EGR vaccum hoses were reversed by mechanic - have just verified this. Also tested EGR - applying vaccum makes car stumble at idle.
Cleaned throttle body.

I suspected it could be a sticking EGR valve (the one on top of the manifold).

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1985 190E - Gone
1989 230E - Gone
1995 C200 - Gone
1993 280E 120000KM - Built like a brick, the best one yet