Thanks to wozzoom and his archived thread about idle issues:

https://www.rx7club.com/2nd-gen-archive-72/faq-idle-problems-334730/

I have been dealing with an idle issue on my 1987 GXL for quite a while. I have just been driving around it. I finally got serious about it because I want to sell the car. I followed this thread and it took a lot of work and frustrations because I really wanted to keep the car stock (My last 2nd gen was a F Prepared autocross car with all emissions removed and everything bypassed... SO EASY TO WORK ON!).

If you have any problems with your idle go ahead and tackle it with the help of this thread. Strip the car down to the block the first time and work your way up. I tried to do uim and tb only and had to tear it back apart again. Luckily I had extra parts from my other FC so I could swap parts as I had questionable resistance. I went further than the thread and put hi temp silicone on every accessory that could be suspect but it was worth it. I have a rock steady 800 RPM idle. This is the first time on any of my RX-7s that I have had a perfect idle. My FD does not even idle this well. I really do not want to sell the car now.

The archives are even helpful to the long time RX-7 owners. Thanks again.

The patient:

 

congrats. just did kinda the same thing but still getting her finished up. DONT SELL

 

isnt it truely amazing what happens when you search?
there is a ton of super useful information, clean s4 man, glad to hear it runs well and idles perfectly.
i did the tear down on my first rx7, passed emissions 0 problem and idled perfectly at 750.
good job!

Lloyd