Hey James look at what you did. reduced the carb air volume 15 to 14mm. This will increase the speed at which the air is entering the carb because the engine still needs the same amount of air. This will cause faster pulling of fuel through the needle. You said if you restrict the air, it idles, you have slowed the air down and it is pulling less fuel. If you lower the needle rod, higher clip setting, it should do the same thing. When it is running wide open, the rod will be out of the picture, does is it four stroke? Maybe the horrible running is that it is four stroking. Just something to think about.