On August 8, 1998, approximately 1150 mountain daylight time, a Piper PA-31-350, N27196, owned by Capitol Express Airlines, Inc., and operated by Air Bridge, Inc., was substantially damaged during a forced landing at Alamosa, Colorado. The airline transport-rated pilot, the sole occupant aboard, was not injured. Visual meteorological conditions prevailed, and a VFR flight plan had been filed for the ferry flight being conducted under Title 14 CFR Part 91. The flight originated at Kansas City, Missouri, at 0733 central daylight time. Both engines had recently been overhauled by T.W. Smith Engine Co., Inc., in Cincinatti, Ohio, and the airplane was being ferried to its home base at North Las Vegas, Nevada. The airplane was then to be placed on the operating certificate of a new carrier, Air Bridge, Inc. According to the pilot's accident report, the left engine lost power as the airplane approached Alamosa. Unable to restart the engine, he feathered the propeller. When he attempted to lower the landing gear, it would only partially extend. He attempted but was unable to lower the landing gear manually. This necessitated a go around. The airplane would not maintain flying speed nor altitude due to the drag from the partially extended landing gear. The pilot decided to make a forced landing in a cow pasture about one mile south of the airport. During the ensuing landing, the airplane sustained substantial damage. On August 20, 1998, the left engine, a Lycoming TIO-540-J2BD (s/n L-4489-61A), was examined and functionally tested at the facilities of Mountain View Aeromotive, Alamosa, Colorado. In attendance were representatives of AIG Aviation and T.W. Smith Engine Co., Inc. The Federal Aviation Administration, Textron Lycoming Engines, and Hartzell Propellers chose not to participate. According to reports submitted by Mr. Ronald L. Ecord of Mountain View Aeromotive and Mr. Myron Carlson of AIG Aviation, a broken coupling bolt was noted on the right side of the turbocharger, preventing the V-band clamp from completely securing the exhaust pipe to the turbocharger. This would allow extremely hot exhaust gases to escape into the engine compartment. The turbocharger transition baffle was found to be partially melted and the manifold pressure line leading to the differential pressure controller was burnt through and was separated. This condition would allow the mixture to enrichen and the engine to flood. Its attachment fitting was also partially melted. Without changing the damaged parts, the engine was placed in a test cell and started. Maximum manifold pressure attained was 29 inches and the engine ran rich at all power settings. To simulate the pilot's action, the mixture was placed in the full rich position and the throttle was closed. The engine quit. The damaged manifold pressure line was replaced with a new one and the engine restarted. Maximum manifold pressure attained was 42 inches. The mixture was placed in the full rich position. When the throttle was closed, the engine did not quit but continued to operate at idle power. According to Textron Lycoming Service Bulletin 240P, dated May 4, 1998, all V-band couplings and gaskets are to be replaced when an engine is overhauled. The failed V-band coupling was found to be rusted and discolored. Its condition suggests it had not been replaced. Additionally, the failed manifold pressure line was made of rubber instead of a flex stainless steel line.