On April 20, 2013, about 1027 Pacific daylight time, a Boeing A75N1 airplane, N985SS, was substantially damaged during a forced landing near Santa Rosa, California. The airplane was registered to and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. The commercial pilot, sole occupant of the airplane, was not injured. Visual meteorological conditions prevailed and no flight plan was filed for the local personal flight which originated from Petaluma, California, about 1000. The pilot reported that while joining up in formation flight with a second airplane, he reduced power to slow his airplane down. As he increased the throttle, he noticed no response from the engine. The pilot stated that the engine was still running, however, movement in the throttle and application of the electric fuel boost pump would not alter the engine's power setting. The pilot initiated a forced landing to a vineyard. During the landing roll, the airplane nosed over. Examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed that the upper left wing was structurally damaged. Examination of the recovered engine revealed that the throttle linkage remained attached and moved from stop to stop by hand. The main fuel system screen contained a fuzzy, spongy material along with other debris. The throttle body fuel screen contained many small particles. Fuel was removed from both the main and lower fuel tanks. Debris was also located within the lower fuel tank fuel sample. The source of the debris was undetermined.