I have a 07 rx8 after rebuilt engine and Napoli ignition upgrade,I am getting a misfire code but car runs fine,any suggestions on cause?

 

Have you tried without the Napol kit, or did this kit work fine before the rebuild? They are not particularly well reputed here.

The other thing to check is your catalytic converter. If it's clogged you will get misfires and/or bogging at high rpm and slowly kill your freshly rebuilt engine.

 

Those Napoli coils look like the same shitty coils that came in my no-name kit (red body with black bracket mount). Three of mine were producing a weak spark and one stopped sparking altogether. My car ran much better after replacing them with Napa Echlin coils.