By disconnecting and connecting the ICV a few times i got the engine to idle at about 750~800. The duty cycle was at 22%. I went ahead and started backing out the mixture screw (3mm allen) and the duty cycle climbed up to 36% (leaner). If i continue CCW on the screw to make it even leaner it doesn't budge from 36% but if i go far enough I stall the engine. When I raise the RPM to 2500 the duty cycle doesn't change more than 0.2%. Any suggestions please?

Update: I took the car out for a hard drive. Immediately after returning I measured the duty cycle as 31% at idle and 37% at 25000 RPM (no load). Based on what I have read this is not acceptable because the difference is greater than 10%. Should I turn the screw richer to get it within 10%. I don't think it will let me go any leaner. What is more important the absolute duty cycle at idle or respecting the +/-10% between idle and 2500?

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1972 450SL
1982 300D Turbo