First, both of our 206’s idle high when we first start them. But after a minute or so, they settle down and are fine. I don’t know why, nor do I care. I’m only concerned how they run on the track and hot. My kart doesn’t like to idle at all, and I’m OK with that too. Our ultra high tech automobiles don’t always behave properly when they’re first started. Why would you expect a very inexpensive, low tech, industrial, rototiller motor to do better?
The rubber boot thing is a none issue to the best of my knowledge. It simply holds the outer throttle cable in the top of the carb. We’ve run engines with and without them and I never gave it much thought.