ok i know there's the s4 and s5 but whats the difference is it the year , interior ,motor etc..... i am just trying to build my knowledge up here

 

At the top of this section there is a thread called Specifications: What did the 2nd Generation RX-7 come w/. Options & standard features

It pretty much covers all the options and US models. Here is a link if you still can't find it: https://www.rx7club.com/new-member-rx-7-technical-256/specifications-what-did-2nd-generation-rx-7-come-w-options-standard-features-782409/

You will want to check the sticky threads found at the top of the section pretty much every time before you post because chances are they have a lot of the information you are wondering about.

Also you can get a pretty good break down of the FC on my website that I provide for reference on the 2nd gen RX-7
http://www.mazdamark.com/about_the_fc.htm