An hour of diagnostic time at your local indy shop would serve you very well and probably save you money in the long run.

If it were my car, I'd check idle air control, fuel pump output volume & pressure, and all my of grounds & electrical connections.

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A.S.E Tech A1,A6,A7,A8 & MVAC 609 + EPA 608

Unless stated otherwise, any question I ask is about my greymarket 1985 380SEL.