What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
While on a return flight from florence to Eugene over mountainous terrain, the pilot experienced a rough running engine during straight and level cruise flight. Contact ATC and declared an emergency. ATC advised closest airport was returning to florence. Pilot elected to not attempt that return flight into a headwind for florence but continued east towards Eugene. Shortly after this decision, the engine began running smoothly. The pilot climbed to around 10,000' to provide more options while crossing the mountainous terrain. As the pilot crossed the eastern edge of the mountains into the willamette valley, the engine began to run rough again. The pilot updated ATC on his status. They advised to continue to Eugene if able. The engine began to run smoothly a couple of minutes later. The pilot landed in Eugene without incident. The pilot and a mechaninc performed an indepth assessment of the entire fuel system. No water was present and no anomolies were found. The pilot has since flown the airplane about 5 hours locally around the Eugene area without any engine anomolies.
As the FAA filed it
WHILE ON A RETURN FLIGHT FROM FLORENCE TO EUGENE OVER MOUNTAINOUS TERRAIN, THE PILOT EXPERIENCED A ROUGH RUNNING ENGINE DURING STRAIGHT AND LEVEL CRUISE FLIGHT. CONTACT ATC AND DECLARED AN EMERGENCY. ATC ADVISED CLOSEST AIRPORT WAS RETURNING TO FLORENCE. PILOT ELECTED TO NOT ATTEMPT THAT RETURN FLIGHT INTO A HEADWIND FOR FLORENCE BUT CONTINUED EAST TOWARDS EUGENE. SHORTLY AFTER THIS DECISION, THE ENGINE BEGAN RUNNING SMOOTHLY. THE PILOT CLIMBED TO AROUND 10,000' TO PROVIDE MORE OPTIONS WHILE CROSSING THE MOUNTAINOUS TERRAIN. AS THE PILOT CROSSED THE EASTERN EDGE OF THE MOUNTAINS INTO THE WILLAMETTE VALLEY, THE ENGINE BEGAN TO RUN ROUGH AGAIN. THE PILOT UPDATED ATC ON HIS STATUS. THEY ADVISED TO CONTINUE TO EUGENE IF ABLE. THE ENGINE BEGAN TO RUN SMOOTHLY A COUPLE OF MINUTES LATER. THE PILOT LANDED IN EUGENE WITHOUT INCIDENT. THE PILOT AND A MECHANINC PERFORMED AN INDEPTH ASSESSMENT OF THE ENTIRE FUEL SYSTEM. NO WATER WAS PRESENT AND NO ANOMOLIES WERE FOUND. THE PILOT HAS SINCE FLOWN THE AIRPLANE ABOUT 5 HOURS LOCALLY AROUND THE EUGENE AREA WITHOUT ANY ENGINE ANOMOLIES.