Responded to your PM.
The 2003 will not work with a 2002 GTS due to the fact that the 03 uses Drive by Wire. The only way you could get it to work is if you swap out throttle bodies also.
On another note, this ECU should definately work with a 2003+ Manual Transmission GTS. It would make a good back up ECU to have just in case something fries yours.
My AC quit working due to the fact that somehow the AC amplifier (located in the ECU) quit working so now I have to replace my ECU.
I'll take $100 shipped OBO, and I will consider trades also.