Don't take this the wrong way, I'm not trying to be an asshole but I find it amusing how many experts their are on this topic. Granted there are a lot of opinions and theories, some even fit, but how many of you have had a #8 failure or actually know someone that has? Probably none, but yet so many know are quick to pass judgement on what caused the failure, a bad tune, he was running lower octane fuel, etc. etc. etc. My car did fail. I denied that I had a tune at first because Ford has trolls on these sites and like anyone else here, I took my car to the dealership. I make my living working on Mustangs so I do know a little about detonation, good gas, bad gas, too much timing etc.
My car failed driving slow, approaching a red light and as soon as it turned green putting it in second and just accelerating. Then the light came on and the rest was history. By the way the car still ran good, just a little miss on light load and idle. I can add a little to a comment someone made in this thread that Ford does know.
While talking to the engineer Ford sent out to see my car, he stated that the stock tune has a margin of correction in it. He mentioned that the "design" (and he did say it wasn't a flaw) of the intake manifold and the heat of #8 requires a specific correction. From what I remember he said something along the lines of 3 degrees of a timing window and that the tuners weren't taking this into account when writing tunes. After dealing with a lot of BS with Ford, and I mean a lot I decided to pull the car apart. I measured the end gap of the top ring and to my "old school standards" .006 is a little too tight for comfort. I don't know why my car broke but I know the tuner has tuned many many many other cars just like mine and yours and hasn't had any problems, but mine did. My piston failed on the outside wall of the block, look at the piston and give me your opinions.