Your going to be looking at between 1 and 2k for that gain unfortunately.
Matched inlets, cams, V6 airbox + bang tidy exhaust (akrapovic, innoxline, piper)
And stay away from forced induction.
Enjoy the car for what it is now, then see if you can afford to go that extra mile. These aren't about 0-60 times (6.9 seconds is not shabby in any case) just linking corners and carrying speed. In these you can carry so much, chassis inspires so much confidence and the geometry is superb for fast road work.