Changing the plug gap will only cure it if that is the problem, which it doesn't sound like.
The best thing you can do is get it fully mapped as it has a mappable ecu, as when it misfires it will give clues as to what's causing it, as emissions are watched.
Could a plug breaking down, could be a dodgy connection, maybe a injector overheating, could be lots, check the usual suspects, cps/connector, phase sesnor, check gaps for both, set plugs to around 0.9mm, I use IK27 plugs, as found the IK31 too cold running.
What are the emissions ?
tabetha