Ive been watching in rear view mirror with head lights behind me. This morning at 2900 rpm no smoke then all of a sudden it just blew acouple of nasty clouds of smoke then cleared up. No noticable change in engine speed. I have noticed this happen to lessor scale from time to time. Of course it has become worse since I replaced cat with pipe. What do I have going on here?? 85 300sd 198K

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1. 1985 300sd Cali. (Irene)
2. Cars in family--
3. 91 350sd converted to 3.0l six
4. 91 350sd
5. 71 220d
6. 92 300d