Hi there
Throttle(butterfly)icing can occur in injected engines as I once took part in the retrieval of a force-landed aircraft powered by an IO-540, which had made a descent thru cloud, aftre having encountered icing conditions.When the crew popped out of cloud, the throttle wouldn't respond and all they could get was idle power.When the cowlings were pulled off, the remains of ice could be seen in the air intake and the engine was soon able to be started and it ran normally.
I would also go along with the suggestion about checking the fuel manifold, as I have also encountered a loss of power associated with a diaphragm failure in the flow divider on an IO-360.
regards
TDD