No, you aren't getting 300WHP out of this car with a tune. Your not getting 300whp without throwing thousands dollars at your car (Bigger turbo, upgraded clutch, and supporting mods).
BTW, 50WHP for 600 bucks is cheap as far as HP is concerned.
If you just want the blow-off like sound, get a PRL CAI or shortram (as said).
IMO, the PRL CAI does have noticeable drone from 2-3K at part throttle. The Turbo sounds it makes when pushing it are quite nice though.
The PRL short ram is just annoyingly loud from outside the car. I haven't...