Hi,
Checked earth and lives to coils and it seemed like live was dropping out so traced back to ignition switch and cleaned contacts.
Anyway it was still intermediately misfiring so scoped cam and crank and went on road test, after about 25 miles (it always takes an age to play up when monitoring) the mil came on and misfire present, watching waveform and you could see cam signal dropping out. Live and earths ok so replaced cam sensor and all ok.
Shane