Guys, thanks for your opinion, but I still think that the glideslope is wrong.
I am a flight test engineer and in real life I have always seen the GS not matching the PAPI *only* in very short final, never before. In our case at LIEO you have 4 reds all the time, even from a long distance and you do have the feeling that you are too low...
I have a long experience in P3D with this issue (present in many sceneries), but there it was easy, I loaded the AFCAD file with ADE and moved the GS to the correct position, beside the PAPIs. In MSFS this is not possible.
Further, the ILS of runway 23 is 3.00 degrees, so I don't see why the PAPIs would not have that angle...