I have an older analog gas analyzer that reads CO% and fuel/air ratio(14:1etc). I put the tester on my jeep to make sure it works.
On the jeep it reads about 4% which is high for a computer controlled electronic fuel injection so I adjust the needle to 1.5% for calibration and move to the mercedes. If I jump the mixture way up it smooths out but guzzles gas and coats the plugs with carbon. It is still very hard to start.
forgot to mention I checked compression and all 8 cylinders are from 125-133 psi.