What was found
FUEL GASCOLATOR/STRAINER ON FIREWALL WAS FACTORY-INSTALLED BACKWARD. FUEL FROM TANKS ENTERED THE "OUT" PORT, FUEL GOING TO CARBURETOR WENT OUT THE "IN" PORT. PORTS ARE MARKED PLAINLY BUT NOT EASILY VISIBLE AFTER INSTALLATION. PROBLEM WAS FOUND AFTER NOTICING THAT DEBRIS CAPTURED BY STRAINER WAS ON TOP OF THE FILTER SCREEN INSTEAD OF BELOW IT, WHERE IT SHOULD SETTLE IN THE BOTTOM OF THE BOWL. GASCOLATOR IS SYMMETRICAL BUT CLEARLY MARKED-SOMEONE JUST GOT IT BACKWARDS.