Yep - I had the same experience with a 96 E230 - was hunting and spluttering. After a 1200 Km trip, and putting up with the rough idle it was running smooth as silk.

Just out of interest, does the M104 from 1993 have an adaptive ECU?

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1985 190E - Gone
1989 230E - Gone
1995 C200 - Gone
1993 280E 120000KM - Built like a brick, the best one yet