I have received one of those carbs where the fuel seat was not pressed in far enough.  I think these are either untested, or failed units they sell.  Cost more for them to take the return than to just ship another.  I have the same running issue, ( not electrical) on two Kohler single cylinder engines SV590.  Either surges badly or runs for short time on 1\2 choke.  I have tried all new gaskets, governor adjustment, and valve lash.  I'm really interested to see what you come up with here.