how to check if manifold has gone?

Hi all, i'm new to this forum. Have just purchased a 4.0 p38 and it has developed a strange noise from under the bonnet, it sounds like a squeal allmost whistle sound when you go past 2000 revs have been told it could be manifold drivers side,or the serpinine belt how do i check? Please help as i have not had much luck with 4x4s of late. Many thanks :scratching_chin: