[aussiblue]

If the inlet manifold is leaking it's usually at the bottom of number 1 or 6 inlet manifolds where they bolt onto the head. The best way to find it is too put a length (1/2 a metre) of windscreen sized tubing in one ear while moving the other end around under the manifold listening for a telltale sucking noise; do this with engine idling both when the engine is a hot and when it is cold as the change in head and manifold temperatures can sometimes temporarily close up any gap between the head and the manifold.