The airplane sustained substantial damage to its left rear wing spar after the left engine caught fire shortly after takeoff. The commercial pilot was not injured. Visual conditions prevailed. The pilot later reported she was 1000 feet agl when she noticed the left engines manifold pressure had dropped about six inches below the right engines indications. The engine was surging, and she thought that the turbocharger had stopped operating. She returned for landing, noting the CHT was reading zero degrees but all other gauges were normal. After landing, the left engine died. She taxied to the ramp. The pilot did not declare an emergency, because she didnt think that she had one. She did not notice flames or smoke, and did not shut down the engine in flight. Initial post-flight examination revealed a broken clamp on the exhaust system.
