Does the 2002 3.0 Trooper citation have a secondary fuel filter ?

Not sure, Trooper is an Isuzu model sold in the states which may or may not be the same vehicle, not sure. As for the fuel filter I believe it only has one. If it has fuel delivery problems it may be the fuel pump failing, or injectors, or regulator that aren't functioning properly. The fuel filter is the easiest and cheapest fix to start, and go from there.