What was found
(CAN) ON APPROACH, THE CREW NOTICED A BMEP FLUCTUATION AND A "COUGHING" NOISE FROM NR 2 ENGINE. AS THE AIRCRAFT TOUCHED DOWN THE BMEP FLUCTUATED A SECOND TIME. ON A POST FLIGHT RUN-UP, THE REFERENCE RPM WAS LOW. FURTHER INSPECTION FOUND THE NR 2 CYLINDER EXHAUST VALVE HAD BROKEN AND THE PISTON WAS DAMAGED. THE ENGINE IS BEING REPLACED.