I have a 190E2.3 (1985), about 140K miles. It runs very rough when the engine is cold (plus there is a loss of power). However, after 15 minutes of warming up, it runs very smoothly. The dealer changed spark plugs (they were not fouled, just worn out), spark plug wires (oxidised), distributor cap & rotor (worn out), overload protection relay (water damaged) and fuel injectors (were old style). He checked the air and fuel filters, did a compression test, all were fine. Inspected all hoses. $1000 later, the problem is still there. PLEASE HELP!!!! what should be done next?

Thanks a lot for any suggestions.

Check cold start valve and/or Coolant temperature sensor. I am not a tech but I think this is the way I would go next. Just a suggestion.