Seems weird being the plugs ..

I have ran both platinums and iridiums @ 20psi with the correct gapping and they have been fine with my EJ205. Unsure of what those part numbers you are quoting mean sorry ..

Sean seems to think the Platinums are the go, had no issues with either plugs on my motor. Just saying keep an open mind with your problem and don't get set on the solution until you are 100% sure as in a lot of cases you'll change the plugs back to the ones you think should work and the problem remains ..

Intermittant issues dude .. they'll do your head in.