Ok here is one to pick everyone's brain, just done a pressure test from my TIP(with breather blocked off) to test for boost leaks and split vac pipes and only thing that I could hear is oil bubbling in the sump. Immediately I thought that the head had blown between a cylinder and oil port but as I write this I'm thinking it is most likely coming from the oil return pipe in the turbo ie through the turbo seals! Might be a no brainer but like to know what every one else thinks anyway. Don't see really how air could get back down through the block and bubble in the oil with non-return valves in place. Thanks, any comments welcome.