As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED ON CLIMBING TO ALTITUDE, EXPERIENCED LOSS OF POWER APPROX, 25% AND OSCILLATION OF POWER AND RPM. STARTED TO SMELL ODD SMELL LIKE BURNING, DUAL ECU A & B FAILURE POPPED UP. ENOUGH POWER REMAINED TO ALLOW RETURN, AFTER LANDING PLANE STARTED TO SHAKE AT LOW POWER. AFTER PARKING SAW OIL COVERING THE BOTTOM OF THE PLANE. COMPRESSION CHECK OF #3 CYLINDER SHOWED 0 PSI. SUBSEQUENT BOROSCOPE INSPECTION SHOWED CRACK AND HOLE IN TOP OF PISTON.