his is something apple shoud take more serious and let user that want to downgrade their Apps do that in an easy way.
The reasons you want to downgrade can be that there was som functions you are missing in the new version, or the older version is compatible with your printer and the new is not, or maybe you just liked the old version better.
An easy way to downgrade both Apps and Systems is something many are asking for.
So I actually figured the problem out.
To anybody having a similar problem this video is great:
The only thing not clearly mentioned in the video is that you need an "iTuneslibrary.itl" file from iTunes 10. Which I happened to have from my old mac.
Hope this helps somebody in the future.