As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING A TRAINING FLIGHT, THE PILOT NOTICED SIGNIFICANT ENGINE POWER LOSS AND RETURNED TO BASE. UPON INSPECTION IT WAS FOUND THAT THE INTERNAL BAFFLE INSIDE THE MUFFLER ASSY HAD COLLAPSED. MUFFLER ASSY WAS R & R WITH NEW UNIT, THE SQUIRREL CAGE WAS INTACT AND PREVENTED TOTAL LOSS OF POWER. TOTAL TIME ON THE MUFFLER WAS 665 HOURS SINCE NEW.