High HC readings come from un-burnt fuel, usually caused by a weak ignition system. By leaning out the fuel system your engine now receives less fuel (hard starting). Have the Lamda control(fuel adjustment computer) reset & the ignition system tested. Sometimes changing engine oil can lower the HC readings due to fuel in the crankcase, esp. if the car isn't driven enough to fully heat up the engine.

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MERCEDES BENZ MASTER GUILD TECHNICIAN
ASE MASTER TECHNICIAN
27 YEARS M.B. TECH