What are the my ECU options for replacement on my S5 and the costs of such.

 

It is a 90 vert 5speed

 

Are you asking which Mazda RX-7 production units will run your engine, or are you asking which aftermarket units will run your engine?

 

Was asking about factory computers, but I'll take info on aftermarket since it's on topic.

 

Here is a thread about factory computers. You can pick them up for cheap in the classified section of this website.
https://www.rx7club.com/forum/showthread.php?t=839364

Popular aftermarket computers include models made by Microtech, Haltech, and Apexi. There are many other less common brands, such as Autronic, MoTeC, AEM, Wolf, and Electromotive. Pricing for the lower-end units is usually about $1,000 to $3,000, plus about $500 to $2,000 for installation and tuning. You can read more about these brands and models in their respective subforums, but it is best to talk to your local tuner about this issue prior to buying anything.