There are couple of things that calculators don't know. In my book number one is power under peak. Strong power under peak will accelerate the car quicker with the same peak power. It's also possible the combo may have less peak than calculated. As for MPH a small frontal area sleek car is going to be better than a large boxy sedan. In my case my car has piked up .3/4 mph since it's initial outing with an air pan, chassis and converter tuning. Timing, jetting, haven't made a significant change.
Doug