Gu patrol petrol 4500

A chip won’t be worth it alone, combine it with extractors and exhaust and it will be a bit better. A quality exhaust l, chip and installation will cost the best part of $3k but I don’t think you will be happy with the power increase for the money.
Best method will be to turbo charge it, you can buy the parts for less than $5k that you can install yourself. They only boost to 5-6psi (the most the standard ecu can handle regarding fuelling) and will transform the car!!! From memory the turbo was a GT35/40 from a turbo falcon.

Disclaimer: this info is from when I looked into it about 10 yrs ago. I bought a used turbo, inter cooler and manifold for $1500, that’s as far as I got when someone crashed into me and wrote my Patrol off!

Before modifying things have you made sure the valve clearances are correct? If no the flow and synchronization of all gas flows IN and OUT of the engine will be stuffed up to some degree, which equals less power and economy.
Does it have decent spark plugs to ignite fuel.
Is the timing correct? probably not and should be adjusted.
Is the airfilter clean and passing enough air.
Is the throttle position sensor adjusted to match the opening of the throttle?
Is the oxy sensor in exhaust reading correctly?
Have you had it checked for any codes in the ECU which may be present and meaningful.
If you have bigger tyres then it will slow and retard the vehicle, using more fuel and less go and less stopping too. It is not much use or sense trying to squeeze more power out of it until any basic problems or anomalies are fixed and made correct.