CG,
I bet you have a tank problem--relationship between tank midline and spraybar. That ended up being the problem with my brothers. We raised the tank (you may need to lower it) and it runs like a stuck pig now. This would be especially touchy in your situation since the motor is inverted.

Sorry to hear about your .46. That's not common with these engines, but I have heard of a few bad ones (like any brand). The majority of them, however, are strong runners.