well, my old car, a gen coupe... had +330whp at once, tuned, big injectors blah blah blah... I would still avrg very high 20's... It would go down to 11-13's if a abused it. I had a tune for 87 octane to but never used it, +94 all the way!
Ive heard good #'s out of the new stang gt's once they pass breakin and do a lot of highway.