BMW Repair: high hydrocarbons, fuel injector cleaning service, catalytic convertor

Question
I own a 1994 525i that has failed emissions test twice due to high hydrocarbons. Have already replaced all coils, all spark plugs, air mass meter, air filter, air temp sensor,o2 sensor, and even change the oil. Test show that HC are high only on low speed idle test, at high speed HC are good, all other gasses are good in both high and low speeeds. Any ideas where to go from here? please help.

Answer
with every thing you replaced you are running out things to try. Is the fuel pressure too high? You may have a dripping injector. I would suggest a professional fuel injector cleaning service. last you may need a catalytic convertor.
              Kimber