If you have a plastic inlet its likely to be a gasket, I got a new one and the leak went away. However the steel pipe that runs under the manifold was also corroded so that started leaking soon after ( probably damaged in the removal of the inlet manifold). I would replace the gasket with a proper spare from MGOC and try that, if you want a more robust fix, replace the pipe underneath while you are in there with a stainless steel replacement.