[17Cruzer]

That's a theory. Tune or something inherent in the engine/intake design causing that particular cylinder to run leaner or hotter than others is another theory. Seems odd that it's #1 in particular, when the Gen 1 1.4T would seemingly break pistons at random when it happened.

Yes to both theories and too high final gear ratio causing high engine loading when accelerating.

 

[17Cruzer]

Gearing's fine...in fact, I'd prefer it to be slightly taller like it is on Ford's 6F35 (shares the same ratios, but final drive is taller). Shift logic might need work, though - it likes to lug around in as high a gear as possible and only really downshifts if you boot it.

The problem has more than one cause....

 

[17Cruzer]

Not really. There's 1 OD ratio in the AT and the rest are quite short. The picking a higher gear when accelerating at low throttle openings is programming. Ford and GM have used this same transmission design in many cars over the years, often with a taller final drive ratio that lets for lower highway/4th gear passing RPM.

Fords 1.5/2.0 Ecoboosts don't seem to have LSPI issues, but they love to rev, run rich air/fuel mixtures, and definitely have programming that doesn't lug around in high gears when accelerating.

Yes, really, and you just stated so. Of course, a better quality piston should have been used as well.