340 popping through carb at low RPM.

RustyRatRod said
You need to remember something. The 1406 gets a LOT of press, but IT IS NOT a performance carburetor. It is an economy carburetor and is calibrated as such. The 1405 is the performance tuned version.

agree, and I'll add usually even the 1405 will need to be richened a tad, at least by my experience