RX-7 EFI system

[Mike Comai]

My friend has an RX-7 (early '90s pretty much standard equipped I
believe) which is running fairly rich. I haven't looked at
it yet but I'm going to help him troubleshoot it later this week.  Does
mazada use a similar system to GM?  Im thinking it's pretty different ..
anyway can anyone give me any advice to troubleshoot it, or insight into
how Mazda setup their sytem on their rotary motor?  I'm guessing it's an
an o2 sensor but I'm not expecting it to be that simple.

Mike Comai