Hey guys, i can shed some light into the matter more accurately. I have a 1.4 (AUA) engine equipped A2 with the 6.5j x 16 rims. Reported weight in the registration is 985 kg. Had the engine flushed several times and replaced all the fluids, cleaned the carbon from the EGR valve and piping as well as the Lambda and MAP sensors (duly required). I have also cleaned the throttle body and the inners of it, by removing the plastic housing and soaking the motor and levers with contact cleaner. There was a lot of dust, dirt and residue on the plastic wheels and output of the electric motor. Noticeable amount of carbon came out of the brushes of the motor. I am adding fuel system cleaner every 3 months to the tank using 95 octane petrol. The most important thing for my A2, at least, is having a reliable power source. If the battery is iffy or undercharged the car is acting up a bit. Audi recommended a 80Ah, local Bosch dealer a 72Ah.
Back to the point, average fuel consumption for the city is 7.5 l/100km or 31.4 mpg before the Sprint Booster. Can't report the 0-100 / 0-62 times, because i can't really be accurate about it due to my floppy gear changes. What i can report though is what the Sprint Booster actually does. Model number for the 1.4 AUA/BBY engines is BDD 151.
Monitoring the measuring values of the engine with VCDS and particularly the throttle position and angle sensors, the engine at idle is at 17-19% throttle load at normal operating temperature. Pressing the accelerator in order to reach 1100 rpm has a peak of 15% so from let's say 18 -> 32-35 % until it settles. With the sprint booster it overrevs missing the 1100 rpm by 400rpm and load is at about 40-45% until the computer calibrates(compensates) it to a lower value. At 50% throttle load the pedal is almost half way to the floor and 97%-100% 1.5 cm from the pedal stop. With the Sprint booster, as i said before touching the pedal translates into 40% load. By the time you reach that half way mark you have everything that the throttle valve & engine can give you.
So two things of importance. Due to emissions management and EGR valve function the ECU has a lag or a slower opening correlation between the state change of the throttle pedal and actual opening of the throttle valve. This remains true for 3000 rpm and lower, if you boot it once the next time the ECU recalibrates and removes a portion of that lag, understanding your need for a faster accelerating vehicle. As soon as you stop acting like that it returns to the default state. So being a hoon will get your A2 accelerating quicker.
Living with it differences: Well it's noticeably more responsive. It gives you the feeling of having more bhp and at about 3500 rpm you feel the mixture getting richer and giving a sizable punch in a more noticeable way than the one you got without the Booster installed. You will tend to find that the car wants to spin its wheels more often than usual, especially on uphill situations or when you give it the beans during mid turn. I usually opt to have ASR turned off to avoid the car getting chocked, when accelerating from the traffic lights as an example. Fuel consumption goes north 1.5 l/100km exactly for the inner city cycle, so 9L /100km or 26.1 mpg. Expect to have the same or pretty much the same highway consumption due to your pedal having a steadier value. Lastly i installed a K&N air filter and in a quiet environment, you can have a bit of an induction noise when accelerating hard-ish. Feel free to ask me anything additional to the matter, in case something slipped my mind.