Power Module, Black Box, Secret Tuning . . . it's a resistor that alters the timing of the ignition. Yes, VW folks have used it for decades, but it's not going to get more air and fuel into the bores so that you can have a bigger explosion and therefore more HP. There may (and this is full of caveats) be a slight increase in how fast your car gets up to max HP, but it's not going to be making more HP. Rest assured you're probably going to have to up the grade of gas your using to avoid premature detonation.