You are right to be worried; that 250HP tune is essentially "piston crack insurance" for a stock 6.4L. The root cause is the re-entrant bowl design of the factory pistons. It features a sharp, overhanging lip designed to swirl air for better emissions, but that lip acts like a heat sink. When you add a heavy tune, your timing is advanced and your EGTs (Exhaust Gas Temperatures) skyrocket, causing that sharp lip to glow and eventually fatigue until it cracks—usually in cylinders #7 or #8 because they run the hottest at the back of the block.
To monitor for early failure, keep a close eye on your blow-by: with the engine running, flip your oil fill cap upside down over the fill tube; if it gets blown off by pressure (the "tea kettle" effect), your rings or pistons are likely compromised. Also, watch for a constant white/blue haze at idle that smells like raw fuel, which indicates a loss of compression.
Honestly, if you want that truck to see another 50k miles, de-tune it immediately to a street or tow file (under 100HP gain). Unless you are ready to drop $15k on a built long block with de-lipped MaxxForce 7 pistons, that high-HP tune is a ticking time bomb.
