[BrandandGeneric]

Maybe, but Mozart was Austrian (...)

That's what modern "anti-German" Austrians would like you to believe. Mozart's father was born in Augsburg, his mother in Salzburg (as Wolfgang Amadeus Mozart himself), which was not even Austrian during his lifetime, but independent, culturally basically a Bavarian territory and therefore a part of the "Bairischer Reichskreis":
http://de.wikipedia.org/wiki/Reichskreis

Mozart was later living and dying in Vienna, yes, but actually that doesn't even matter as German speaking parts of Austria during the 1700s were as German as the Rhineland or Hesse (or otherwise we also have to call Goethe a "Frankfurtian" and not a German poet )

(...) and only German thing there that I can think of is German language, brought by German nobility. Natives were Slovenes and Czechs.

Yeah, the famous Slovenes and Czechs from Salzburg.... hmpf

Same goes for you - Bavarians. You are German only because you live there, but your closest ethnic relatives by far are Czechs.

Even the name Bavaria (Bayern) comes from Boii, which was the recorded name of local (supposedly "Celtic") tribe, and also the Latin name of Czechia - Bohemia (Böhmen). Now, I don't know what Boii means in Germanic or Celtic languages, but I do know Slavic word Boj - battle (schlacht), Bojar/Bojary (Russian medieval nobility), Bojovnik - warrior (krieger) etc. You can make the picture yourself.

History is a bunch of lies, unfortunately.

That's a laughable theory, just like your pan-Slawism (especially if one thinks about the many wars and little solidarity between various Slavic people). The Boii were Celts, who indeed gave this region their name, but they were absorbed by Romans (some of them also lived in Gaul and N. Italy) and Germanic tribes. It's obvious that you don't like the fact that Slavic people arrived rather late "on the stage". Trying to make people believe the Boii were Slavs is about as absurd as all these funny theories that you would hear from Turks.