whats the subcooling? whats the temp. diff across the filter drier? whats the temp. diff. across the king valve? if you think there is a restriction there, i would check for refrigeration effect.
another trick i've learned from a guy, was to run the condenser, but disconnect the fan control. watch the distribution tubes (in the evaporator) and make sure they all ice up evenly. if one doesn't ice up (or ices up slowly), it's not getting refrigerant.