Engine high idle problem

The catylitic converters are dirty or the EGR system is dumping a lot of unburnt hydrocarbons back into the system which is too much for the catylitic converter.
Both components either need to be replaced or cleaned. You can find catylitic converter cleaner that you add to gasoline at mosr auto parts stores, but if it is too dirty it will not work very well.
The EGR may be cleaned but with the mileage yyou have the vacuuim actuated diaphragm is probably old and has failed. It is supposed to only dump exhaust at higher RPMs and when it is always open it gives that sulfur smell.

Amen- Doc