Sorry for all this detail, but it is a complicated system. I stopped at 11 points til you catch up.

1)I think you are saying the throttle valve is a little open. You said: "I did have all the linkage off and started FROM DEAD CLOSED TO just off the stop and brought all the other linkage to meet that position," and "when I first put the system together the only rpm it knew was 4000."

1)It should be DEAD CLOSED. Its not a carborator. The computer controls all the air at idle. And, the 4000 happened once you fixed all the vacuum leaks because someone used the throttle to compensate for the leaks. I can'r explain how it does that. But now you should have the dash vacuum gauge pegged on economy. Really good vacuum. The engine had a lot of air coming in and good vacuum and that pulled the gas plate down raising the engine speed beyond where the idle system could control it.

The screw on the throttle butterfly is there only to prevent the butterfly from sticking into the aluminum throat. It should be totally closed and even bit just a little. Benz fuel injection has always been that way.

2)ALL the idle air needs to be controlled by the icv. Except for the little bit coming through the bypass tube in the rubber fittings at the input and output of the icv.

3)When you adjust the mix too lean with the allen screw, the vacuum will pull the big air plate down a little and you will hear the sound of air flow increasing past the plate. You should try find that point with the allen screw and back off from there to 700 to 750rpm, air is not noticably coming through the plate, smooth idle, no hunting.

4)Remember that the O2 sensor output changes with exhaust temp and sitting at idle and playing with the mix allows the exhaust to be cooler than real driving. In fact when cold starting (with the sensor cold) the computer opens the icv to give an idle of about 1000rpm, (everything else set about right) until the signal gets into range from the O2.

5) To find the not-too-lean point, turn the allen screw CCW 1/8 turn at a time until you find it. You have to wait for the O2 sensor/computer to catch up and stabalize with the engine. Idle should stabalize in just a few seconds. I think it gets worse taking longer, as you get too lean leading to hunting. Once hunting lean, go back 1/8 at a time, waiting for the computer to stablize. Until you get 700 to 750, air is not noticably coming through the plate and no servoing.

It sounds like you know how to do this and are very close if not too lean already. Check it, drive it, heat it up, stop and put it neutral or park, if it hunts, pull over and quickly try 1/8 turns CW.

6) I can't tell you how rich to go. You want to be far enough away from hunting lean enough to save fuel and have good emissions. Hopefully someone else here has experience of where to leave it before you check the emissions. The mix adjustment will repeat well (the allen will be in the same position each time) and all within only one turn of the allen: go too rich, the idle goes above 800, too low and the idle drops to 600.

7) 600 seems to be a computer limit, once there the hunting gets worse, but rpms won't go lower. I think this adjustment should be set so the idle is about 700 to 750, air is not noticably coming through the plate and no servoing. When you get too lean with the allen, go back 1/8 at a time until the idle is stable: no stumbling sound in the exhaust, no sound of harsh sucking through the air plate, rpm 700 to 750.

8)The hunting is due to the O2 sensor and computer changing the air too far and then changing it the other way too far. The system tries to self-adjust (hunts) to try to keep the engine from stalling or idleing too high. I'm not sure, but I don't think the gas is servoed at idle. I think its just the air flow through icv that is under computer control. The icv is big enough to control all the idle air the engine needs.

Its normal for the O2 system to look around a little for the best setting and older engines never have a perfect best setting, the .4 volts at pin 3 X11, will move around +-.05V as the O2 sensor roams around making sure its keeping the air about right for the gas flow.

9) The .4 volts moves around as the O2 sensor/computer adjusts the fuel ratio with the icv. The voltage at the icv is the result, adjusting the air in this 'closed loop' idle system. The input is the O2 sensor.

10) My vacuum at the EZL does the same as yours. There is a "dongle, (computer term)" R16. Its a plastic plug connector with no wires coming out of it back next to the brake booster. It controls the 5* setting with vac off. The normal value of R16 is 750 ohms.

11)I'm unclear what the vac-off timing should be, I don't have the manual for this car. But vac-on timing has to do with idle speed, mine was up at 30* with 950 rpm idle and 12* at 700 rpm.