I have made good progress dialing in my timing on my 78 L-82.  I followed Lars recommendations on setting total mechanical advance and the engine responded well to this.  The only thing I still notice is I have a little 'chug' during off idle driving.  I suspect I am getting to much vacuum advance.  I don’t see any numbers on my advance pot to identify what I have but I get about 10deg. of advance when it’s active.  I’m thinking of getting an adjustable vacuum advance pot.  Does anyone have experience with these and do they work?