The aug issue of 4x4 Australia reviewed the used jackaroo/trooper models from 98 using the 3L 4JX1 engine. I'd like to quote some interesting points:
1) The caterpillar HEUI system relies on oil pressure to run the injection. By 70k km, many of these holdens were hit by troubles, beginning with leaking O-ring seals for the injectors. Caterpillar provided revised O-rings for isuzu to retro-fit, and in most cases it seemed to work.
Bottom line: anything built before Nov 3, 1999, was subject to a recall to fix it, so make sure this has been done.
2) The type of oil used is crucial, too. The injection needs low-viscosity oil to pressurize properly, especially when the engine's cold, so the recommended 5w-30 or 5w-40 synthetic is not negotiable. The wrong oil not only makes the jackaroo hard to start, but may lead to O-ring problems.
3) To compound the Holden's injection issues, the engine isn't very tolerant of bad diesel fuel. It can get smoky, lose performance and suffer seal failures- all the things that became difficult for subsequent high-tech diesels when they encountered our crook fuel in australia.