With a bone stock FD3S (US spec) 5-speed car, would a Power FC with FC Commander and Boost Control Kit do me much good? Is it an ideal place to start before modifying the RX7 to ensure you tweak out the maximum performance with each additional part you add later?

 

Would eliminate the 3k stumble right off the bat and if you or someone close can tune then yes you can tune it as you mod it.

Boost control kit would only be helpful if you plan to really turn up the boost later or go single turbo (and use the PFC to control boost).