Having cast pistons does make it weak...under lean conditon. If the engine leans out, you get about 5-7 seconds of abuse on a cast piston before the top ring land cooks off. A forged piston will last somewhere in the time range of 15 seonds.

That engine dead from not have enough fuel. Those injectors where just outa there flow range. I have cooked 2 sets on cast/hyperutectic pistons with n20 back in the day. My pistons looked exactly like that.