Friend's going to order New GTS arriving soon!!What Mods should he add??

[Supercharged Vipermad]

600 wheel HP? Find a good tuner. I think only the TNT guys make >600 RWHP in a normally aspirated Snake, and it's a beast (see Car & Driver review); Hennessey's Venom 650 makes ~550 RWHP.
Is your friend sure that he's willing to make the compromises it takes to get a car with that much HP? I've owned a 620 RWHP car, and it wasn't a particularly good street car...

Cheers,
Ben

[Fred(DrivingSchool)Kinder]

The first thing to do is take a Skip Barber (or other good) Driving School. If your friend has an order number they can get a 25% discount on the 2 day Performance Driving School. And a 10% on all other Skip Barber programs. I suggest the following:
2 day school, a couple one day Car Control Clinics, the Three Day racing School, "Viper Days" to enjoy the performance in a well controlled program. Stay tuned by doing Lapping Days and taking more Car Control Clinics. If your friend can master the stock 450hp/490ft/lbs then pick one of the several Viper tuners to give the Snake a little brake cooling and high temp brake fluid(do the brake stuff before going on the track). Then you can think about HP. If you are on the West coast Dan Cragin at Claude Short Dodge is a good place to start. Couple points of interest many new owners of performance cars never make the trip home from the dealership. A skilled driver will run circles around an untrained driver, with a 100 more HP, on a road course. This I have seen many times!