When forced induction is applied to the combustion chamber of an engine, the resistance across the gap of a spark plug increases.  The greater the amount of boost, the greater the resistance.  There comes a point where the factory coils cannot produce a large enough voltage across the gap of the plugs at the right time to initiate a spark.  A couple solutions to this include narrowing the gap of the plugs (from the factory spec of 0.044" to about 0.030") or modify the ignition system to control stronger coils, or at least a combination of each.  Thanks to several folks on the MiataPower list and in the forums, we were able to figure out how to get stronger coils running in a miata application.

The links below show the procedures for this modification on miatas I've worked with.  

1991 Miata w/ Link ECU: MSD/GM coil packs

1994 Miata w/ Link ECU: MSD/GM coil packs

Here are is the parts list thanks to those that contributed to this modification:

Part Number required Manufacturer Part Number Source Approx price (US$) Notes
Coil 2 MSD 8224 $40  
Coil interface module 2 MSD 8870 $27  
Igniter 2 MSD 8364 $68  
Waterproof case 1 Hammond Mfg. 1590WDD $19  
8.5mm Spark plug wires 1 set Magnacor "Vishnu Performance spec wires"

Call the directly at 248-471-9505
Ask for Steve and mention the Vishu Performance spec wires

Hook-up wire

black 14ga, 15ft
black 20ga, 2ft
white 22ga, 2ft
yellow 22ga, 2ft
red 20ga, 2ft
blue 14ga, 10ft 
green 20ga, 5ft
orange 20ga, 10ft

    Autozone, Advance, or Pep Boys
$4 per 30 foot roll  
MOSFET N-channel transistor 1 Radio Shack 276-2072 Radio Shack $2  
1/4 watt 470ohm resistor 1 Radio Shack   Radio Shack <$1