This is where you are wrong, I have ran a completely stock all wheel drive 92 talon at the track, and ran a 15.3 at 89 mph. Then I plugged in the pro efi unit(which takes about 5 minutes) and ran a 14.2 at 95 mph. The factory has a completely different goal when tuning a stock production car. They are looking for smooth driving, emission, and general appeal, so the average person (anyone from 16 to 60 years old male or female) can get into the car and get smooth appealing drivability. When tuning for performance this is not possible to achieve. When obtaining maximum performance gains, transition between gears and throttle response is more immediate, and therefore less "smooth". Milage can also be increased with a stand alone. 14.7 is ideal for emission output, but a car at cruise can easily run at 17 to 1 air fuel. I have seen cars go from averaging 19 mpg to 24 with a properly tuned stand alone system.