ummmmm bro sorry to break it to ya but the GTS doesn't have a turbo. The one turbo kit that has been made for the celica gts is made by xs and cost upwards of 6 grand to get done to your car and anyone that has shown interest for the kit xs and for some odd reason gave them the run around. The only turbo GTS i know of is the one owned by alt wheels and that was XS's demo car. there is supposdly a gts running around in new york somewhere with a custom turbo on it, but i can tell you if it's true it wasn't easy for him due to the lack of room and the 11:5:1 compression ratio and the lack of aftermarket support the celica has been getting.
also a celica with a 50 shot and a turbo would blow the hell out of it's motor. anymore than a 50 shot on the gts and your asking for trouble.
i don't think you mean turbo when you say it, your probably talk about the gts' high lift cam (kinda like vtec for hondas) lobes that enagage at 6k and give a nice like in the powerband. as you can see in the dyno below, but i don't really see how it'd be very easy to mistake it for a turbo kick, the both have 2 very different feels.
also what the heck are you talking about nitrous alwasy hurts N/A engines more than turbo ones?
viper if you thinking about putting nitrous on a N/A supra a 50 shot should work fine without a problem, i don't know about anything higher than a 50 shot since i've never played with the N/A supras and don't have any specs in front of me.
What car exactly are you thining of putting nitrous on? if you let us know we could probably give you some good reccomendations.