I had the same problem on mine, athough I have a 603 I'm sure this may help.
here is a link to the thread. Although I was told by a tech that my injectors were okay when I had them pop tested two turned out to be bad.

1987 W124 300D rough idle and smokes

__________________
Owen

87 300TD 603 I-6
94 Jeep XJ I-6 4.0 (see the pattern)
89 750il
seventy-two hundred feet above sea level (kinda cold up here)