Safe cheap bolt on power on the stock ECU:
Single fogger wet efi kit, RPM window switch, mechanical WOT or TPS switch, fuel pressure safety switch.
Jetting is one of those up in the air type things, personally I wouldn't run more than a 50 shot on a GT-S, but many have ran more successfully.
Now you can always go from there with engine management, get a good solid tune for the juice, run multiple stages, direct port, run progressive controllers etc etc etc.