Yes I had thought that the rpm drop was due to that but I have not had an older car for a while so I thought the drop was a bit high but then again the older cars due drop more.

I have had a suggestion that the cold start injector could be staying on which is giving the over fueling smell and the higher idle all the time.

Where abouts is the injector on the engine and can it be checked by taking a voltage reading on start up and then one after the car has been running for a while?