You can not swap a 4gxx into a GT/GTS. You would need to swap the entire drivetrain along with having to rewire the entire engine bay and swap ecu's. Far too much work and too costly. Your better off starting with a rs/gs and either turbocharging the 4g64, which handles boost very well, and swapping the sohc head for an evo 8 head OR swapping the engine completely for an Evo 8 4g63. The Evo ecu is also a direct swap for most 2001 Eclipse rs/gs models and all 2002-2005 eclipse rs/gs models.