An amendment to my post above; the level of HC (hydrocarbons) should be one of the main factors for leaning of fuel distributor. My 380SL seems to behave best at around 150 to 160 parts of HC. The value of leaning that is best for idle attitude is sometimes referred to as the 'sweet spot'. Don't let someone tell you that to enrichen the distributor adds more power. Better behaved at lean is the better of the two. Besides, there is no such thing as 'power' in my 380SL.
I have my '96 LT4 vette for that.