Not qualified enough to say mate, they are factory forged of course but who's to say whether aftermarket pistons would have avoided this.

At the end of the day 'shit happens' and I made an assumption that backfired on me. Lesson learnt. I booked some time off work so am pulling the engine this week and taking it to Doug, and fingers crossed I'll have it back and running before Xmas.
And yes if ppl want to know the tuner they can see my bug thread but my main point is that I don't believe the piston failed purely as a result of the tune.

Moral of the story is if you make even a small change to your exhaust ie gutting cat or going high flow cat and you are running a tune... Go get a retune.