The Stang Analyzer is just an estimator.
What it comes up for isn't written in stone. There are so many things that it cannot figure on when judging how quick you can run the 1/4 based on hp.
Lizard King, I would bet your car is making better than 260hp stock, factory performance can differ +/- a good few percent. 5% difference would mean 13hp on a new GT. I doubt ram air is giving you more than 10hp. Your time picks up about a tenth, right? That would be closer to 10hp than 25.