Their making some pretty big HP and Torque claims there. I would give Rob a call at Cape York Automotive Cairns and Dyno run before and after just to ensure your Hilux is safe and also if the claims are real.
You have purchased a really good vehicle there with a very good engine and for around $180 a before and after Dyno run will protect your investment ---- and yes Rob is a straight shooter so he will tell you up front maybe even before you purchase the exhaust if its worth it.
Here is a link to the Cape York Automotive website
http://www.capeyorkautomotive.com.au/services