Well I want to MOD my 2004 Grand prix GTP Comp g Get a PCM and a pulley upgrade but i am not sure what i need to get in order to do this. I know i need A PCM, smaller pulley and tighter belts. I am not sure if i need anything else from that. My car is stock it has the paddel shifters, and i dont know if they have a PCM especifically made for a comp g. Basically i would like to know if i have to mod engine before adding this parts in. So i guess my question is what do i need in order to get an upgrade PCM and Pulley and where can i get it?