Power cutting late in the day at the drag strip
Yesterday I was at the drag strip with my for the most part stock 2012 Mustang GT (axle back exhaust, Shelby wheels and PSS tires). I had AdvanceTrac shut off (stability and traction control were off). I had 20+ runs and my best one was the third run. After the 3rd I filled up and never seem to get close to that again. After filling up I was consistently getting 13.5's. A few times though later in the day, at launch, the car would just bog down. At first I thought it was my tires getting good grip and I just didn't rev it up high enough to launch. But it got worse and worse to the point where it felt like it was starved for fuel, like a computer was killing the engine for half a second. Then it started happening at the beginning of second gear also. I looked down to confirm that the AdvanteTrac was off. I still had half a tank fuel and it wasn't cutting power on me when it was at 1/4 tank before filling up. Any ideas as to what caused this?
2012 Ford GT Premium. Stock. It's a bad ass car as it is so I'm not in any hurry to mod it.