I used this code:
http://opengauge.googlecode.com/svn/...no/mpguino.pde. You have to modify it slightly to work on the Passat's fuel consumption signal. Find this line in the code:
attachInterrupt(0, processInjOpen, FALLING);
attachInterrupt(1, processInjClosed, RISING);
and change it to:
attachInterrupt(0, processInjOpen, RISING);
attachInterrupt(1, processInjClosed, FALLING);
More info on it
here and
here.
Good luck!