The best thing for you (and your car) is to realize it is a vn V6, they have enough torque and the car is light enough to play through the first and second gears comfortably, and generally a constant climb in third to 180 - 200 (on a straight road).
But the v6 doesn't put out large amounts of power, and from memory of working on a few project VNs you couldn't push more than 175kw @ the wheels until you upgraded:
Push Rods
Springs
Oil Pump
Leave your VN the way it is and learn how to drive the vehicle as an entity better. My VN Commodore has had nothing but a 2.5" catback sports, an actual SV3800 memcal & computer + loom & dash from my mates SV3800 wreck, and a K&N air filter, but the difference is I've looked after my car & constantly keep it serviced & running on the best fuel.
Truth be told mate, there isn't much you can do with a VNs 6 cylinder for worthy power gains without reaching far into your pocket. One day I was walking throught a carpark after work and saw a man standing next to one of the most immaculate VN Commodores I had ever seen, not a bolt unchanged and he popped the hood and there stood a stroked 4.4L with a Watercooled Supercharger (running 6psi at the time) and he said when he uses his drag pulley and has the charger on 14-16 pound (Which the block struggles to handle as is with a .6L volume increase) the end result was around 200-220HP at the wheels.
I advise you pump your money into keeping the car safe and roadworthy & doing up the exterior and interior until you get your black license and then f*** the 6 off and drop an Aero motor (I think they're called, I believe they are a 6.3L V8) or drop an LS1 / Original Holden 5L.