you mean the bent stem of the valve, after the cylinder got lean so ran super hot after detting and theheat found a weak point in the valve head for it to fall off and smahs you pistons up

id imagine the bent stem wasbecuase of whats left of the vale head being thrown around in the chamber and your engine revving still at high rpm lol

but it is shit when it happens as its happened twice on me on my old rs turbos

when you get a new engine go efi