BE60 pilot reported engine failure due to broken intake value resulted in a critical equipment problem and divert with priority handling to safe landing.

Narrative

Aircraft was on autopilot at FL210 when a slight shutter occurred in the left (#1) engine followed by a loss of manifold pressure from 30' to about 17'. I disconnected the autopilot and proceeded to verify the dead engine and then feathered and secured it. I notified ATC of the engine failure and that I was diverting to ZZZ. I trimmed the aircraft and began my descent. During descent I briefly attempted to restart the engine; but stopped after to two brief start attempts and re-secured the engine. I landed the aircraft uneventfully at ZZZ in VMC conditions and taxied off the runway on to the adjacent taxiway. A tug brought the aircraft to a shop on the field where the engine was visually inspected. No external issues were identified. Upon pulling the top spark plugs on the #1 engine there was physical damage to the #2 cylinder spark plug. A bore scope revealed a broken intake valve on the #2 cylinder; all other spark plugs appeared to be in good condition. The oil filter was removed and inspected for metal. Some small metal pieces and flakes were observed in the oil filter.