Dazza's-STi

Ok team, this isn't a scoob engine but as great minds are often found in this area I was hope for some ideas from my fellow SNers

I've got a problem with the Atom Honda engine, its developed a misfire that happens as the load increases, more than 1/3 or 1/2 throttle and it feels like fuel starvation... its also missing the odd beat at idle too, but seems to run ok on light loads... Any ideas team???
Oh and it has the supercharger fitted also but this all seems ok...

Any help greatly appreciated...
Ta

Daz