One of the best things you can do before parting with your hard earned is part with a little cash and put your Patrol on a dyno and have its power output checked i.e. power output at the wheels!
Anyway they should give you a print out of a performance graph - easier to read than a heap of figures.
If you've got your doubts about the injectors, about $500 will get you an exchange set. Maybe do that before the dyno. Also, check that the injector pump timing marks are aligned. If no timing marks you will have to have the pump timed - 0.74mm is the displacement.
Depending on where you go, the shop doing the dyno test for you might be able to tune the Patrol by
chrome exhaust tips emissions.
Once you have a fully tuned Patrol (assuming a decent exhaust system), then decide whether or not you need a turbo. Keep in mind that you may have to have the Patrol dyno tuned again after the turbo instal. Don't depend on the installers to get it right and if you do the job yourself, part with the extra to have tuned right.