TIS stands for Technical Information System.. it's basically the software you need together with a Gm Tech 2 Programmer to do all thouse firmware updates on your gm vehicles and configure new Electronic parts to work with your car. usually the gm dealer has those things..
TIS used to be on a, i think, annually released DVD and now they provide it over the internet and call it Tis2Web ...

at least that's what i understood from googling around

here's a link that takes you to the free part i mentioned.. this allowes you too "look up vehicle configurations" .. whatever this is good for.. as i noted above, it is only a guess that this information might be helpful to reprogram you radio for euro frequencies..
TIS

cheers
pascal