How do i tighten up my manifold for my m reg clio?

I have quite a loud noise when drivng which i thought was the exhaust. But i was told that it was the manifol. For £40 a mechanics managed to tighten it up and take away the noise but only temporarily. So i need this done again but as this might be a regular thing i don't want to keep paying the £40 nor do i want to fork out the money for a brand new one.