stock internals i say 100whp over stock and it stays a reliable daily driver. the further you go the less reliable it becomes. i've tuned some to 150whp over stock w/o probs, but you're rolling the dice. with rods, pistons, headstuds-the sleeves are good for 400-500whp on a good tune...i usually say 400whp to give yourself a good margin of error. i've tuned a few on stock sleeves past 500whp that held fine, but i wouldn't expect much if you go that far.