Agree with 04GPGT. Tune alone isn't going to give 75hp. I think in the fine print for most companies they will say - "with supporting mods" and by that they mean at least air intake, downpipe and maybe catback exhaust. Some might include a lower temp thermostat or even sparkplugs.

You can get as much HP as you want on these cars, the question is whether you really want to drop the $$$ into all that's necessary to support having it run safely and on a daily basis.