I've had a simular problem where my engine was missing at higher rpm. In fact, I really didn't notice until I got it up on a dyno and saw it on the graph. I had previously had the car dynoed 2 weeks prior and was surpised when I took it back to the dyno and it was down 25hp.
It turned out that the metal piece in the cap that contacts the rotor had fallen out and the rotor was arching the gap.
Replaced the cap and the motor gained 25 hp...
Samurai
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I'm a racer...at least that what I keep telling my self at night when the lights out, the engine is cold and the wax is calling my name...
I've learned the line is an ellusive thing, easily shown, but rarely remembered.