You mention the inlet manifold is OK - however i have had a ticking noise when my exhaust manifold gasket failed (down pipes to exhaust) the ticking noise was caused by spurts of gas leaking through the gasket - new gasket cured it - however the engine sounded a lot more throaty/noisy.
Also ticking may indicate a faulty timing belt - not sure of the set up on the V6 but in the 1.8t the belt is drivers side