On September 18, 1998, approximately 1400 mountain daylight time, a Piper PA-28RT-201T, N8252S, was substantially damaged when it collided with poles during a forced landing near Duck Creek, Utah. The commercial pilot, the sole occupant aboard, was not injured. Visual meteorological conditions prevailed, and a VFR flight plan had been filed for the personal cross-country flight conducted under Title 14 CFR Part 91. The flight originated at Canyonlands Field, Moab, Utah, approximately 1300. In his accident report, the pilot said he was in cruise flight at 12,500 feet, en route to Las Vegas, Nevada, when he noticed the manifold pressure had dropped from 51.8 inches to 25 inches. "The engine had poor response to throttle movement, and the engine sounded bad when I moved the throttle." The pilot made the decision not to proceed further due to the remote terrain. As he checked his maps for the nearest airport, the airplane lost altitude. The pilot said the "engine did not seem to have much power, and I was about 3,000 feet AGL by this time." The pilot made a forced landing on a dirt road. During the landing roll, the aircraft struck poles next to a cattle guard, causing substantial damage. According to the salvage company and the FAA inspector who examined the engine, two of the four screws securing the rocker cover on the number 3 cylinder were missing, and oil was leaking out. The rocker cover had a round indention on the outside, and a wear mark on the inside. The exhaust rocker arm studs were also loose. The rear stud was only finger tight. Aluminum was found imbedded in its threads. The front stud was loose, but its nut locking mechanism was still in place.