Why did you back out the idle screw ?
I'd first suggest, as usual, that you ensure your timing and dwell are spot on as any adjustemnts are futile without this being correct first. Then ensure the venturi plate is fully closed, take the air filter rubber hose off and peer in. After this ensure the linkages are set correctly as per the details in the "How to" section !
If you've done the above and still have a high idle then try turning the air screw on the inlet manifold all the way in. This should stall the engine and if it doesn't then you have a vacuum leak, air is being drawn in somewhere, either at one of the fittings or gaskets.
Regards,
Ben in Ireland.
'64 230SL 4sp.
'03 CLK Kompressor