So, this morning I reflashed my ECM with a few tweaks to the timing that Rick Crawford had suggested for me (since I switched from Mids to Long Tubes), and drove to Wal-Mart for a fund raiser my class was doing. The car was running like normal, I even let it rip through first and second shortly before pulling into the Wal-Mart parking lot. Not a single issue. I got there a little early, so I rolled up the windows or turned on the A/C. A few seconds later the engine shut off. This has never happened before. I cycled the key and tried restarting the car. It cranked but wouldn't manage anything but a sputter here or there. There was no CEL or any other warning lights. Eventually after about a dozen or so tries, the engine wouldn't even turn over. I started to smell something like burnt wiring. Immediately I thought that I had either burnt up the starter motor, or it had just seized from over heating. I had my friend try to give me a jump with his 2012 5.0 (not proud of that) and still nothing. A few hours later we pulled the battery and took it to Auto Zone to have it load tested, and recharged. After 20 minutes and passing a load test we took my battery back and installed it. It started to turn over again and sputtered, then nothing again. I talked the guys there into letting me try a new battery and if that wasn't it they would take it back. New battery installed and no difference. So, I called USAA and had the car towed back to my house. I reflashed it with the tune I had before just to see, and nothing. I had also pulled all the plugs to make sure there wasn't a stuck injector dumping fuel. I've checked all the grounds, and everything looks good. When I cranked the car the voltage went from about 12.4 to as low as 9.3-9.4 volts on my battery. I have heard that the ECM won't let it start with less than 10. If that was the case, then why wouldn't it work on a jump?
So, starter? Or is there something else I should look at. The car will be sitting for the rest of the night. Thanks for any help you guys an offer.