The broken stud itself isn't visible as it's hidden behind the heat shield, but the failure evidence is there. On the close up photo above the dipstick and just to the above/right of where the three small hoses are clipped, you can see a lot of dry black sooty deposits. This is escaping from the front of the exhaust manifold (rather than going down the exhaust) so there will be a gap in the exhaust manifold gasket sealing the manifold to the head. Very likely (almost definite) culprit is a broken stud rather than a simple gasket failure, but you could be lucky
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. thanks geoff. 
