Welcome to CHR. Hope you enjoy a long stay here.

You say that you "...cleaned the carb really well in a parts washer..." which makes it sound like you maybe did not disassemble the carb and rebuild it, but rather just cleaned the outside? Is that right?

If your power loss is fuel related I would look to the in line filter being plugged vs ignition, but your comment about the melted filter element points to a question of a back fire. Maybe pull the filter element and see if it improves with unrestricted airflow?