The simple explanation is that there's a big gearing leap in that 5-speed auto between 3rd and 4th, causing it to drop-anchor a bit right before the traps when it shifts to 4th. Don't expect mball to be able to rationalize how that all works out to a 13.6 @ 99.9
The gear ratios of the ATX are 3.22 - 2.29 - 1.54 - 1.00 - 0.71
For an '05 Mustang GT with ATX and 3.31 rear end ratio, the max. speed in 3rd gear is 95.3 MPH (assuming the trannie shifts at Ford's published redline of 6,000 RPM). That means the ATX GT will be shifting from 3rd to 4th gears right at or before the speed trap & finish line. Add to that the fact that the PCM retards the timing during the shift and the trap MPH makes perfect sense. It also says that this mother hauls ass off the line.
I can't wait for some good GT MTX #s as according to M/T the MTX they drove had fuel cut off at 6,200 RPM . That means a MTX GT could hit 106 MPH in 3rd gear (3.55 rear end & 1.33:1 3rd gear ratio). I suspect the fastest way to run yout MTX GT in the 1/4 will be to wind it out in 3rd and let it hit fuel shut off as you cross the line.
But a reality check here for the average driver. A ford engineer told me that they had a little drag race session among some of the engineers. He said that most of the guys were faster in the ATX. However the really good drivers made the MTX cars go faster than the ATXs.
What the **** is an EVO??? You know what, never mind. I don't care to know. It could run in the 10's from the factory and I wouldn't give it the time of day. I think someone on this site is suffering from TMFAF. (Too Much Fast and the Furious.)