Magnum 330 Gas In Airbox

Other posts indicate its a needle and seat issue but I don't feel like this is? If the needle didn't seat wouldn't gas flow out of the overflow drain on the bottom of the carb?

One thing that came to mind was the idle mixture screw. A new one didn't come with the rebuild kit and I damaged the O-ring that was in the carb while removing. I replaced it with one that looked as close to the original as possible.
If the O-ring was not the correct size, say too small, would it leak and allow excess fuel to go somewhere? Like the brass jet you see in the picture? Just a wild guess.