To answer Scott's questions...
I've got an '07 car, with 32k miles, and the following power mods:
RPi induction system
Active Autowerk ECU tune
JVT headers (SuperSprint copies)
SuperSprint uncatted section1 (s-pipe)
SuperSprint section2 (x-pipe)
SuperSprint race mufflers
3.91 final drive upgrade
My car put out peaks of 311rwhp @ 8000 rpms & 256rwtq @4024 rpms.
Upped from stock baseline peaks of 266rwhp @ 7265 rpms & 236rwtq @ 4552 rpms.
Total horsepower gain = 45whp
Total torque gain = 20wtq
With all the money spent, I'd say NA tuning has
not been worthwhile thus far
Good thing I got some of the stuff for free (or at least for really cheap), and did most of the labor myself to save money
