Those seem to be big pieces to be going very far in the engine. I would suspect something dropped in the head during the last servicing that fell down the oil galleys (maybe got broken up banging around the valves in the head?) I drained my oil and played the 'what is this?' mystery metal game a while back with some interesting bits I found, pretty good sized pieces of piled-up material (ferrous metal.) I tore most of the engine down (heads off, pump out, rotated the pistons, checked the main bearings, pulled the rocker arms and lifters, removed most of the oiling system, all of the fuel system, the air compressor, etc) never found a darned thing. Engine continues to run like an absolute champ. Best of luck to you.