One of the greatest areas for improvement on the stock Mazda rotary (besides perhaps the intake and exhaust) is the ignition system. I've spent lots of time on this side of the engine, and I've got to say that Mazda, like all the other automakers, likes to save money where they can. But then again, it's got to be reliable. Well over 100,000 miles are possible on the stock ignition components like ignitors and distributors. Of course plugs, caps, rotors, wires etc obviously need to be changed every now and then, but that's a given.
The point is that the stock system is more or less ok for stock power levels, and will function ok with intake and exhaust mods for more power, but improvements to this system, even if everything else is left stock (or modified), will always help.
Here are some articles I wrote about doing ignition mods.
Here is something else that has helped me. Check out the fun way to test ignitors and coils
Here you can see the progression from MSD to DLIDFIS on my REPU.
Here's my Cosmo.
I haven't finished it yet. Too many other things to do at the moment.
The firing order of a 20B is actually quite simple. It is basically 1-2-3 (spaced 120º apart). Just remember each Trailing plug fires 15º after its Leading plug and you're all set. That's not complicated at all!
The part where it gets complicated is in trying to get the L/T split to work with most common timing computers. Some out there can do it, but I'm not looking to spend that kind of money. Infact, I've seriously considered getting one of those RB 20B distributor kits for $550+ or whatever the price is, simply to keep it simple.
But then again, I'm sure I'm a little smarter than that. I bet I could design and build a 20B ignition system in the spirit of DLIDFIS, which would not only walk all over any kind of distributor cap and rotor system out there (like RB), but would also perform similar to those expensive timing computers, yet still might surpass them in certain ways. Hmm...