I strongly suspect that it will be the exhaust manifold blowing. Is the engine remapped?, this can make them very susceptible to this, the exhaust manifold warps with the increased engine temperature then breaks several of the mounting studs causing the screech by way of escaping exhaust gas.
Simple check, look under the heat shield above the turbo and exhaust manifold on the right side of the engine as you look at it from the front.
Are all 10 nuts present on the exhaust manifold? Is there signs of soot around the joint?
If so then im afraid its the manifold. This has happened to me twice, hopefully now cured. The first time the manifold was replaced with a second hand one from a breaker and the broken studs replaced. It lasted about 2 years then same again. I decided that I wanted a permanent fix and did a bit of research about it. There are loads of threads and opinions on the best way to do this. Pricey tubular fabricated manifolds, ceramic coated manifolds to help the heat from warping it, cutting out the webs on the cast manifold etc etc. What I have done is bought a secondhand manifold that previously warped but which has been skimmed on a milling machine making it true again. The generally accepted wisdom is that once it has been heated to the degree that it has warped that the molecular structure has changed permanently and further heating at similar temperatures will not affect it again (some may disagree?). Then it was fitted with an uprated stud set from JE Engineering which provide a better clamping method. So far so good. I put my warping down to 1, remapped engine - provenance unknown as it was done before I got it and 2, long towing at motorway speeds with a big twin axle caravan.
Hope you get to the bottom of the problem!