I was looking into replacing my restrictive S5 Air flow meter with some other type that may have the same output readings

i found this link where they use a S4 AFM on a Miata
http://www.miata.net/solo/airflowmtr.html

i and going to seriously look into finding something that ahs more CFM

i think the S4 is rated @ 300CFM but do not know what the S5 is.

 

Check this out.... it may be an alternative

http://www.pro-flow.com/Gallery%20Fi...0mm%20ProM.htm

 

this is sort of the page we need for the RX7 AFM technical break down

http://www.roversd1.nl/sd1web/airflow.html

 

just saw this too

http://www.pro-flow.com/Import/import%20front.htm

 

The chances of finding a bigger AFM that has the same output characteristics are basically zero. For starters you need to find a flapper or sliding-cone type, not a hot-wire type. Very few engines more powerful than ours used these AFM's

You'll definitely need to use some type of fuel computer to properly calibrate it's electrical output. If you just slap a bigger AFM on, the ECU will just see a lower airflow reading and not inject enough fuel.
BTW, stating "the S4 AFM is rated at 300cfm" is meaningless. Airflow readings must be quoted with the pressure used to generate that airflow or they're useless.

That basically is the info for the RX-7. The Mazda EGI system is a licensed version of the L-Jetronic system described, and uses pretty much the same AFM.

At the end of the day if you swap a bigger AFM in you might get 5-10hp at best, and you'll still be stuck with an antiquated EFI system. Save your pennies for a modern EMS instead, and not only will you get a vastly more capable system, you won't even have to worry about an AFM.