Brett
In your case you need to be careful of a poorly fit main needle. I won't say worn because it is a new engine. When the engine is running touch the main needle, like put a little side pressure on it. If the engine changes rpm you have a loose needle that is causing most of your problems. You will have to fix that before you can make since of anything else. The loose needle doesn't cause an air leak it just allows the fuel metering to wander all over. I have noted that the needles on my OS91s seem to wear a little fast. A piece of tubing over the needle reduces this wear. Often folks put tubing over the needle to stop air leaks. Often there is no leak, the tubing just stops the needle from wiggling.


Denis