What kind of upgrades could I do to increase the performance of the car rather than replacing the motor in it?
My car has an automatic transmission.
Hello - the most straight-forward swap would be to the 3.8 liter supercharged engine (L67) offered in 2004-2005. Make sure you get the transmission controller out of the donor car as well. The basic transmission (4T65E) is the same, but different controller. Other engine swaps (like going to the SS engine) are possible of course, but get much more complicated quickly. Good luck!
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