Hi Don;

See message #6, 2nd pic from the bottom.
Mazda RX-7 Crank Angle Sensor (CAS) Inputs to Megasquirt I.
   http://www.rx7club.com/showthread.php?t=658411

.01 uF cap across the G+/G- wires near the EC2

Here is a page on grounding RX7's:
   http://www.aaroncake.net/rx-7/grounding.htm

Cheers
Cary