I have a bit of a strange bug. On the final i only have 3 PAPI lights and on the short final i have 4 PAPi lights (pictures).
It's possible you can't see the lights well because of the distance and your anisotropic filtering settings, because they are custom (not using the default FSX PAPI system) and are affected by that like any other texture. Be sure you have Anisotropic filter enabled in the video card Control Panel.
Also the Runway 33R, 26R and 8L do not have any PAPI lights at all (but i guess the real airport missing the lights too?)
They don't, according to the current Jeppesen charts.