i remain corrected, the egr system with the air pump and egr valve started in 1991 which is the year of my 190E 2.6 which is interesting. Emissions until 89 was controlled by lambda.

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)