I thought I'd throw my 2d in here. I had a Honda '89 CB900F a while back, lovely bike, ran beautifully except for an annoying 'stumble' at 3000 rpm. After reading up a bit on it I bought a pair of green 3ohm coils from Z1enterprises. They worked out considerably cheaper than buying the same coils from a UK seller, arrived really quickly and were well packed.
Fitted them, fired it up. Those big, fat juicy sparks were doing such a good job that it was idling 1000 rpm higher than with the old coils. Took it for a spin and it was like a new bike. Much smoother, better pick-up and more powerful all through the rev range. And the stumble had gone completely. Major result.
Those old coils were from 1989 and had clearly either deteriorated or were just plain inferior to the Dynas, I'd thoroughly recommend them and am only waiting for a better exchange rate before getting a pair of the black 5 ohm coils for my K7.
