What was found
PILOT REPORTED ENGINE STARTED MISSING AT 15,000 FEET FOLLOWED BY SURGING THAT MADE IT NECESSARY TO SECURE ENGINE. TROUBLESHOOTING FOUND NR 5, AND NR 6 CYLINDERS HAD 12-18 PSI COMPRESSION. PULLED CYLINDERS AND FOUND EXHAUST VALVE BURNED IN BOTH CYLINDERS. CAUSE IS MOST LIKELY ENGINE HAD BEEN OPERATED AT TOO LEAN A MIXTURE.