88 S4 N/A .... Ok, the backfiring and loss of power is evidently being caused by the wrong voltage on the trailing spark plugs coming out of the coil. After diddling with it for a few minutes now she is back to not starting. I have an extra coil and swapped it out with no difference so the problem is originating somewhere else. The Mazda dealer has no RX7 tech any more so who has some ideas on possible causes. Thanks in advance for your ideas.....