Welcome!
The 3.0l engine is actually tuned extremely well from the factory. BAV Autosport has a power programmer for your car, but as you have found, you will not get more than 8 - 10 hp if you are lucky. That is barely noticeable and would shave .1 - .2 sec max off your 0 - 60 time.
To get more performance you will need bigger mods such as cat back exhaust, new intake, etc