I already posted the solution that partially (I can use perseus kernel only) solves my baseband issues.
point 1: if the i9305 EFS does not contain any personal data (i.e. IMEI that is stored in the NV Memory).. somebody could kindly upload his EFS image?
In case you are not comfortable in sharing his EFS, it would be a good starting point to know which files and folders are contained in it.
point 2: in my case the issue seems to be related to the BOOT.IMG (perseus kernel is replacing this partition only). According to this consideration my question would be: which kind of differencies there are between the custom boot.img (perseus) and a stock one? files? permission? drivers?
they are different in size... perseus is bigger...