What was found
PILOT REPORTED THE FUEL PRESSURE PEGGED MAX PRESSURE CAUSING THE GAUGE TO BECOME INOP. IT WAS REPLACED AND AGAIN THE GAUGE WENT TO MAX & BECAME INOP, THE FUEL FLOW AT FULL THROTTLE NOW EXCEEDS 30GPH INDICATED WHERE IT USED TO BE 28GPH & ALL THE CYLINDER HEAD TEMPERATURES IN CLIMB ARE COLD WITH THE HIGHEST TEMPERATURE BEING 320 DEGREES, LEANED OUT IN CRUISE, CHT'S WOULD BE AROUND 280. AFTER THIS FIRST EVENT THE ENGINE BEGAN SURGING INTERMITTENTLY AFTER ABOUT 20 HOURS SINCE OVERHAUL. AT THE TIME I INSPECTED THE AIRCRAFT, THE ENGINE WOULD START NORMALLY AND IDLE SMOOTHLY AT 500RPM. AFTER THE ENGINE WARMED UP THE IDLE INCREASED TO 850RPM, POPPING WAS OBSERVED FROM THE EXHAUST, AND ENGINE DID NOT RUN SMOOTHLY. DURING FLIGHT CHECK, THE PLANE FLEW NORMAL TWO LAPS AROUND THE TRAFFIC PATTERN, THE THIRD CLIMB OUT THE ENGINE WOULD BEGIN SURGING INTERMITTENTLY AND INCREASE IN INTENSITY & DURATION UNTIL LANDING. UPON LANDING THE ENGINE WAS INSPECTED. THE ELECTRONIC IGNITION SYSTEM WAS FOUND TO BE TIMED CORRECTLY WITH NO INSTALLATION ISSUES, NO INDUCTION LEAKS WERE FOUND, THE INJECTORS WERE REMOVED, CLEANED, FLOW TESTED, & REINSTALLED. AFTER SEVERAL ENGINE RUNS, I COULD NOT GET THE IDLE MIXTURE SET CORRECTLY. WITH THE ENGINE RUNNING & RPM SET TO 800 AND AGAIN AT 1000RPM, THE MIXTURE THUMB WHEEL WAS ADJUSTED FROM FULL LEAN TO FULL RICH WITH ONLY A 20RPM INCREASE NOTED & NO CHANGE IN THE ENGINE ROUGHNESS. THE FUEL INJECTOR SCREEN WAS REMOVED & FOUND CLEAN. THE FUEL SERVO WAS FINALLY REMOVED AND THE THROTTLE PLATE WAS FOUND TO BE EXCESSIVELY LOOSE. THE ENGINE OVERHAUL SHOP WAS CONTACTED AND THE FUEL SERVO SENT IN FOR WARRANTY EXCHANGE.