I just spoke with Horizon Hobby. If it is more that an air leak with the HSN o-ring or carb o-ring they want me to send it in--which I will do since I don't want to compromise whatever warranty comes with it. The fuel lines are solid with fuel when running and the engine seems smooth all-around. I just remembered that it ran good for a short time when I moved the HSN closer to the carb. Maybe it's not sealing right again and is sucking in some air there.

Thanks for your help!