So initially, when my ignition was set up, I reviewed George's Duraspark schematic, and saw that he uses the "official" Duraspark Coil (an oil-filled type), and an associated ballast resistor.
I set up my system initially with the ballast resistor but I decided to use the TFI (solid state) coil.
What I found was that at high RPMs, with the TFI coil, and ballast resistor, I would get an unexpected miss. It really disconcerting. I thought it was bad "lots of things" (wires, dist. cap, Duraspark module). What was funny was it would occur starting at high RPM, last for a while (until I stopped the car) and then start up and run fine, until the next time I got to high RPM.
I finally figured out that by removing the ballast resistor from of the circuit with the TFI coil, I solved the high RPM misfire problem. It seems to me it affects the charging current needed on the e-coils.
I just left the resistor in there, because I mounted it so nicely on that panel. The coil is bypassed by just shorting the two leads together, and tucking it into one of those harness sleeves.