Working on a 05 6cyl. The engine makes a loud squealing noise at 2800 RPM and around 1800 RPM power braking. It is not the belt or pulleys. Already tried with belt off. Someone did a head job and replaced the rockers and rods. The noise is coming from the left side of engine (side where EGR is and facing radiator). Replaced EGR tube and redo upper and lower intake gaskets.