1996 Mazda RX7

Engine Performance problem
1996 Mazda RX7 Two Wheel Drive Manual 95000 miles

initially my engine misfires when it reaches 5000 revs, after installing new plugs, second hand plug cable n coil and a new Apexi power fc ecu, the misfires hasbeen delayed to 6500revs at dyno at 280hp. What can I do to stop the misfire n push it to its red line limit? I planned to push its power band to 400hp, what are the modifications needed and is it reliable?
February 9, 2009.

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