Flightgear (and probably X-Plane) appears to have a runway 06 ILS set at 49° (for a 55° runway), resulting in approach offset that seems much greater than in reality.
In real life in 2007, LIRN's Rwy 06 ILS (NPC at 110.15 MHz) had a 3° offset at 53° (magnetic) whereas the 06 runway was at 56° (magnetic) in a region which had a 2°E magnetic variation in 2007 (J*pp*s*n LIRN chart).
In Flightgear, I notice that runway 06 is shown on FG's map at 55° corresponding, I suppose, to the 58.03° true heading provided in TerraSync/Airports/L/I/R/LIRN.threshold.xml
Notice that in Debug/environment/magnetic-variation-deg = 3.4168 (which is probably correct although the 40,000 km3 of magma below Naples confer a magnetic anomaly to Naples, helping make it a very attractive city to visit in real life ).
Flightgear's Naples NPC ILS is listed in Navaids/nav.dat.gz with 52.736° which, I suppose after subtracting the magnetic variation, provides the 49° value indicated on the map. The offset from runway 06, instead of being 3° is 6°.
Where does the 52.736° value come from? I have the impression that someone entered an magnetic heading (close to 53°) into the Navaid database instead of entering a true heading that should be about 58.03° (runway 06 true headng) minus 3° = 55.03°.
What do you think?