What was found
(CAN) RIGHT ENG WAS SHOWING HIGH MANIFOLD PRESS AT LOW RPM & A SPLIT FUEL FLOW INDICATION FROM THE LT ENG. SEVERAL THINGS WERE TRIED BUT THE MP PRESS REMAINED HIGH. NR 3 CYLINDER FAILED A COMPRESSION TEST DURING DIAGNOSTICS, SO UPON REMOVING THE ROCKER COVER THE INNER & OUTER EXHAUST VLV SPRINGS WERE FOUND BROKEN. DUE TO THIS ALL THE ROCKER COVERS WERE REMOVED FROM BOTH ENGS & 3 MORE SPRINGS WERE FOUND BROKEN ON THE LT ENG. COMPRESSION CHECKS & GND RUNS HAD BEEN CARRIED OUT IN THE PAST FEW MONTHS WITH NO ISSUES & THE ENGS RUNNING WELL. THE ACFT HADN`T BEEN FLOWN FOR AROUND 18 MONTHS, ALTHOUGH IT HAD BEEN KEPT INSIDE DURING THAT PERIOD.