First problem was the break fluid faries absconded with all my fluid, that was simply a union not done up properley when i fitted the new BMC. Second was the car developed a missfire at about 6k, tried a spare set of coils, still there, made sure i had no boost leak, no problem there, finally i changed the plugs on the off chance (they looked fine) and that cured it.
The plugs all looked much of a muchness and not that old, but one looked like this

With yellowing on the white ceramic bit below the blue ngk writing (sorry cameraphone pic).
What causes this? Is it a dodgy plug or am i on my way to a more serious fault?