The upgrade is worth about $1800AUS fitted. This includes a completely new exhaust and a modified air box. The extent of modifications done to the air box depend on the trucks's usage. If you are staying on hardtop with little dust, then the most modifications are done and the greatest gains are achieved.
Also the standard exhaust is far from optimised. I've experienced the results of the upgrade and you can't achieve those increases in power and torque by simply changing the breathing of the motor, if the standard setup is already optimal.
The only problem is, more performance....more throttle....more fuel! You can get consumption savings with this upgrade if you drive easily. But face it, you've just installed more horses, the temptation will be to use them!