M103 low idle speed, vacuum issues causing a misfire?

[blue85']

This is my first gas vehicle in over 10 years. It is a 1988 300E in very nice shape, body wise and interior wise. Yet it failed emissions so was put up for sale. Older lady owned it and put maybe 200 miles on it a year.. for the last few years.. The tank has been drained and refilled with fresh gas, and a injector cleaner.

I've done a tune up, consisting of a cap, rotor, plugs, wires, IAC valve hoses, and tested the other small hoses connected to the intake manifold.

Runs ok at speed, but stoplights are not much fun. HOT idle is about 600RPM in neutral. Vacuum is about 13 inches, and at the moment the car is at 5600 feet above sea level.

Headed out to pull the Over Voltage Protection Relay, and test for vacuum leaks ... as I am telling myself that low vacuum is part of the problem.. (I have all ready ruled out the brake booster, and 5 vacuum ports on the intake manifold) Testing the fuel injectors next.

Guessing there is no idle speed setting on this motor.. and that the low idle speed is ether vacuum related, or something else is out of whack.

I am open to suggestions, on this particular issue, as well as general instruction on how to come up to speed on the CIS fuel injection system/engine management...