You cannot "chip" a celica ecu like you maybe able to with other cars. The resistor or "speed chips" wil actually be canceld out by the stock ecu. The celica ecu adapts to the resistors and after driving it sets you back to stock.

For an 00-02 GT or GTS a apexi pfc is you best bet. emanage or hydra are the only things right now that work on 03+ gts but i think u think said u have an 02 gt so thats not an issue. Like everyone said with proper tuning with the mods you have, your going to get . . . 5 hp not worth the grand+ for the pfc and tuning.

Next question is, is it an auto gt? If so i am sorry to tell you, your going to need significantly more money to make it reasonably quick. Though the auto GT-S is actually slower the an auto gt (issue with lift/weight/low end torque) the auto GT is almost a waste to make it fast. You would have to loose the wing, subs, amp, heavy 18's and work on removing parts on the inside to make a dent.

Unfortunatly the 7th gen adds, "Looks fast" really lives up to its name on a GT and prettymuch gts as well