Frustrating isn't itI dre lol, I've been all over the engine and mine seems to be coming from the centre, rear of the cylinder head, from what I have researched it could be a small exhaust manifold blow, (I'm not convinced of that by the way it sounds) or an injector seal in the fuel rail, I think my next step will be to have a look at them, if I find any thing i will let you know