it's not smoking, loosing a bit of water, no mixing of the oil and water as i said it's just like the water/compression side of a head gasket failure. found a place in liverpool that apparently can hot test the head so i'll probably get that done as i've no access to some of the equipment to do all of your tests but can pressure test and leak test. i took it out when we had some rain the other night to see how much power i'm loosing and in first when turbo came on full boost 18psi instead of the normal loss of grip that we all expect it made all noises but it was if some of the boost was going somewhere else and felt a bit like a standard turbo on 6psi and no loss of grip. have you ever come across cracked blocks as i might put the other head on which will rule the head out altogether, shame your not closer