majority of aftermarket parts claim "up to XX hp" and they usually base those numbers on in combination with other aftermarket parts or tune, however because you are tuned you would maybe gain those numbers.
I probably wouldn't go any higher then 3.31 in an auto unless your planning on forking out cash for a good set of tires or you plan on turning your car into a pure drag car.
as for TrackApps I don't know how accurate they are I have done quite a few 1/4 runs and it says my all time best 0-60 is 2.3 which is impossible with my mods lol
best idea of your 0-60 is run your car down the strip and use your time slips, fair amount of calculators out their can base your 0-60. A guy on the corvette forums made
an excel sheet you input your time slip numbers and it determines your 0-60.