MMD, yes had the head skimmed last time and it was flat. EBS41, I've read threads on your set-up and wondered why I had issues with mine! I've got standard AU head, 1.6 copper gasket, 9psi boost, water injection, run 98 octane, 250rwhp. Sorry, don't know details of ignition advance, only that motec has a 'safe' tune by a reputabe tuner in Brisbane (Masterson performance).

After all that, it appears the head gasket is fine at this stage (other than not a perfect seal...slowly uses water). Had car diagnosed today, and its the blower, not making any boost. There's no strange bearing noises (had it rebuilt 40 000km back), so I'm guessing must be a broken internal belt. Time to get it pulled apart again!