design overview 03 to 05 engine were 275HP net and 275 lb/ft torque.
06 to 07 were 291 HP and 277 ft.lb net.
08 to 09 were 285 hp
(" For 2006, power was increased to 291 hp (217 kW) at 6000 rpm and torque to 277 lb⋅ft (376 N⋅m)) at 4800 rpm with the addition of a MAF and a complete internal redesign of the engine; however due to the new SAE rating procedures ratings can vary slightly between years 06 to 09. ")
With a cat delete and tuning its not hard to add 10-20 HP.
The single biggest gain that can be had is using the 06 up head and porting it.
