Do you need insulin for yams as they are a vegetable (I'm not talking about sweet potato)
Personally, I would take insulin for yams as it's a higher amount of carbs kind of vegetable and do treat them as I do any kind of potato. I'm inclined to take some for most veg when I'm being inactive, but not bother when being active.
You might prefer to eat some yams, then test two hours later, to see what the results are.