I'm sure the stock pistons/rods can hold more than 350whp with the right setup and VP C16 fuel. The Honda's have made upwards of 550whp on VP C16 with stock pistons/rods. The 2AZ-FE block itself is STRONG. I've personally seen 60lbs run through the stock block with pistons, rods, billet mains, billet main girdle, etc.