Engine Buzz 307 Xsi - frank_butcher
Engine makes a loud buzzing sound at around 2800-3000 revs. Fine either side of that.

There's not much room in the engine. I can't follow where the noise is exactly coming from.

Is this likely to be a blowing manifold or just something which is rattling and needs tightening?
Engine Buzz 307 Xsi - Altea Ego
just something which is rattling and needs tightening

yup

plastic engine cover, manifold heat sheild, exhaust heat sheild something like that