Update: The best I could do with R16 was 300 ohms gave me 0 tdc with no vac. Vac on still pulls timing up to 12. Idle was still about 900. Not sure this is the way it should be, at least its closer.

Got brave and adjusted idle mixture at the air horn. CCW leans so I went 1/4 and got a nice reduction in rpm. It took 3 or 4 of those 1/4 turns (slowly and waiting for stabilized idle) to get too far, a rough stumbling idle. Good news idle came down to about 600 and timing down to 10.

Looked at signal at X11 (I think pin 3) with ac meter and pure rms meter. My scope would'nt trigger on this signal. It would trigger on pin 1 but I think that is tach signal. Voltage started near 5V and came down to 4.1 (about 70%) where I left it. That point is about 1/2 turn from where I had the 950 idle. It is very repeatable. idle is about 700, timing is still 12 advanced with vac. Vac off drops to the R16 setting of 0tdc.

One more: I found a post on adjusting the mix on a 91 560, that discribed a button and LED on a diagnostic connector back by the battery. Mine doesn't act that way. With the ignition on and engine off, led is lit, pushing it does nothing. With engine running led is off but pushin button turns it on only as long as button is pushed.

What next.