You don't seem to understand that, it's not a "single" addon that cause OOM errors, it's the COMBINATION of EVERYTHING you have at an airport and, most important, your settings.
First, having more than 4GB will help, but more than 6GB will probably won't make any difference, since FSX can't allocate more than 4GB, and the remaining 2GB should be enough to run Windows itself.
If you have OOM, which usually happen only with very complex airplanes, is because your settings are too high, try lowering the "Scenery Level of Detail Radius".
With KLAX, a memory saving feature is to turn off HD Textures, at the cost of image sharpness.