Decrease spark dwell time, improve firing?
Spent most of my days on Mazdaspeedforums.org when my Speed6 was my daily driver. One interesting idea a couple of us came up with was instead of upgrading the coil on plug system with a proper 4 channel CD ignition system, we tried to improve the coils themselves.
I'll see if I can pull/take pictures soon. I believe our car, like most non-sport NA engines, we have a narrow band primary O2 sensor. So pretty much anything at WOT is out the window for recording, measuring. Most cars are tuned to be very rich in these scenarios and in worst cases, too rich (safer than too lean!)
Most of the guys who have installed at least a CAI will see more uppen rpm power BECAUSE the stock tune will go fairly rich at WOT, the new intake giving more air, will lean that out and possibly give a leaner, better a/f ratio for power. I'm sure if you WOT a lot in this car you will see VERY dark, carbon fouled spark plug tips (on the outer edge for rich WOT).
Now after all of that precurser, here is what we did: replace the COIL on plug boot wires that touch the spark plug with those of lower resistance. The stock aluminum ones are good but I remember they still showed a couple mili ohms or something of resistance. Replaced it with a copper strand (not coiled but meshed) and the resistance is about 1/4 of the stockers.
May be breadcrumbs but since I'm sure everyone has some copper wire sitting around somewhere they aren't needing (need maybe a foot for the entire project), it is relatively a cheap mod. Idea that this would improve the most in higher rpm instances where the spark is weaker, slower to ignite. Yes, I know COP is much better than previous ignitions but why not? Getting a more efficient burn at idle and at WOT is a good thing. The knock sensor on these engines (prob same on the Mazda's, so VERY sensitive) will pull things back if any pinging is noticed.