There are many definition files. They are specific to the ECU part number, software version and also the programs that use them. Some are compatible however, a Tuner Pro definition file won't work with WinOLS and vice versa.

You need to know what your ECU part number/(sw/hw version) is and what program you plan to use to make the changes and then look in the ECU definition files section of this forum. The easiest way is to put your ECU part number in the search box and the results will show up. You may have to create one for your ECU but I doubt that, it being from a '01 jetta because chances are, there is a def file for your ECU already on here.

If this is still somewhat confusing or just rose alot of questions, go to the Wiki section here on NeF or the S4 wiki.

if its a aww engine code its a 032dl..