the main fuel mixture is adjusted at the pressure sensor , the idle mix at the knob on brain , PERIOD .
The issue at hand is the thing running like crap while at rest. To adjust the idle and how the car runs at idle, the fuel/air mixture is adjusted at the ECU.
for a number of tech articles on the matter, and the attached, first page, section H.
Idle speed is adjusted by the idle air screw.
You WILL effect the idle speed by fiddling with the ECU knob, but as a result of misadjusting the air/fuel mixture. Doing so will compound other issues and contribute to poor engine performance at idle.
Once the running-at-idle is sorted out, and you see how the car runs while under normal operation, adjusting the pressure sensor will effect how the car runs. There are testing steps, also located in http://www.benzworld.org/forums/vint...sources-4.html
, but they require the use of a specialty Bosch test set that I've yet to find on eBay, etc.
The pressure sensor can be adjusted using an exhaust gas analyzer (the procedure and gas values are also put up online). You're more likely to find the analyzer at the DMV or repair shops that specialize in older cars. The pressure sensor is not too awfully finicky, and can be "ballparked" with trial, error and more trial. Misadjusting the thing will cause you to run lean or rich at operating speeds, and will have a marked effect on gas mileage.