I have heard your load/no load method in reference to getting a good read on the spark plugs. But I dont see how it applies to the stumble off idle. If it does it in my driveway, I think it would do it on the street too. Only one way to find out though !

for your second comment (?)...I dont see how that relates to anything.

From what we saw, it looks like it is right on as far as the mixture goes unless I can be told otherwise. I was thinking also (not good when I think sometimes) that my plugs might be black because of the idle time? Maybe they havent gotten hot enough to burn off the carbon?? Just guessing here...